An Etymological Dictionary of Astronomy and Astrophysics

A change in one of the variables (such as temperature, pressure, and concentration of various species) that describe a system at equilibrium produces a shift in the position of the equilibrium that counteracts the effect of this change.

See also: Named after the French chemist and engineer Henry Louis Le Chatelier (1850-1936); → principle.

A change in one of the variables (such as temperature, pressure, and concentration of various species) that describe a system at equilibrium produces a shift in the position of the equilibrium that counteracts the effect of this change.

See also: Named after the French chemist and engineer Henry Louis Le Chatelier (1850-1936); → principle.

A metallic chemical element; symbol Pb (L. plumbum, of unknown origin). Atomic number 82; atomic weight 207.2; melting point 327.502°C; boiling point about 1,740°C. One of the oldest metals used by humanity, because of its relatively low melting point.

Etymology (EN): O.E. lead, from W.Gmc. *loudhom (cf. O.Fris. lad, M.Du. loot “lead,” Ger. Lot “weight, plummet”).

Etymology (PE): Sorb, from Mid.Pers. srub “lead;” Av. sru- “lead.”

A metallic chemical element; symbol Pb (L. plumbum, of unknown origin). Atomic number 82; atomic weight 207.2; melting point 327.502°C; boiling point about 1,740°C. One of the oldest metals used by humanity, because of its relatively low melting point.

Etymology (EN): O.E. lead, from W.Gmc. *loudhom (cf. O.Fris. lad, M.Du. loot “lead,” Ger. Lot “weight, plummet”).

Etymology (PE): Sorb, from Mid.Pers. srub “lead;” Av. sru- “lead.”

In a → sunspot group, the first spot to form in the direction of rotation and the last to disappear. It is the largest, the strongest in magnetic intensity, and the closest to the solar equator among the group sunspots. See also → follower spot.

Etymology (EN): From M.E. leder(e), O.E. lædan “cause to go with one, lead,” from W.Gmc. *laithjan (cf. O.S. lithan, O.N. liða “to go,” O.H.G. ga-lidan “to travel,” Goth. ga-leiþan “to go”); → spot.

Etymology (PE): Lakké, → spot; pišrow “leader, forerunner,” from piš “in front, forward, before”
(Mid.Pers. pêš “before, earlier;” O.Pers. paišiya “before; in the presence of”)

• row “going,” present stem of raftan “to go, elapse, glide by, depart” (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- “to go; to attack”).

In a → sunspot group, the first spot to form in the direction of rotation and the last to disappear. It is the largest, the strongest in magnetic intensity, and the closest to the solar equator among the group sunspots. See also → follower spot.

Etymology (EN): From M.E. leder(e), O.E. lædan “cause to go with one, lead,” from W.Gmc. *laithjan (cf. O.S. lithan, O.N. liða “to go,” O.H.G. ga-lidan “to travel,” Goth. ga-leiþan “to go”); → spot.

Etymology (PE): Lakké, → spot; pišrow “leader, forerunner,” from piš “in front, forward, before”
(Mid.Pers. pêš “before, earlier;” O.Pers. paišiya “before; in the presence of”)

• row “going,” present stem of raftan “to go, elapse, glide by, depart” (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- “to go; to attack”).

One of the organs, usually green and flat, growing from the side of a stem or branch or direct from the root of a tree or plant. A leaf constitutes a unit of the foliage, and functions primarily in food manufacture by → photosynthesis.

Etymology (EN): M.E. leef, lef; O.E. leaf; cf. O.S. lof, O.N. lauf, O.Fris. laf, Du. loof, O.H.G. loub, Ger. Laub.

Etymology (PE): Barg “leaf” (Tabari, Gilaki valg, balg; Kurd. belg, balk, Semnâni valg); Mid.Pers. warg “leaf;” Av. varəka- “leaf;” cf. Skt. valká- “bark, bast, rind;” Russ. volokno “fibre, fine combed flax.”

One of the organs, usually green and flat, growing from the side of a stem or branch or direct from the root of a tree or plant. A leaf constitutes a unit of the foliage, and functions primarily in food manufacture by → photosynthesis.

Etymology (EN): M.E. leef, lef; O.E. leaf; cf. O.S. lof, O.N. lauf, O.Fris. laf, Du. loof, O.H.G. loub, Ger. Laub.

Etymology (PE): Barg “leaf” (Tabari, Gilaki valg, balg; Kurd. belg, balk, Semnâni valg); Mid.Pers. warg “leaf;” Av. varəka- “leaf;” cf. Skt. valká- “bark, bast, rind;” Russ. volokno “fibre, fine combed flax.”

In a calendar, having an extra day or month inserted.

Etymology (EN): O.E. hleapan “to jump, run, leap” (cf. O.S. hlopan, O.N. hlaupa, O.Fris. hlapa, Du. lopen, Ger. laufen “to run,” Goth. us-hlaupan “to jump up”), of uncertain origin, with no known cognates beyond Germanic. The noun is O.E. hlyp (Anglian *hlep). Noun in leap year, so called from its causing fixed festival days to “leap” ahead one day in the week.

Etymology (PE): Andarheli, from andarhel, verbal noun of andarhelidan, andarheštan “to insert,” from andar-→ inter- + helidan, heštan “to place, put” from Mid.Pers. hištan, hilidan “to let, set, leave, abandon;” Parthian Mid.Pers. hyrz; O.Pers. hard- “to send forth;” ava.hard- “to abandon;”
Av. harəz- “to discharge, send out; to filter,” hərəzaiti “releases, shoots;” cf. Skt. srj- “to let go or fly, throw, cast, emit, put forth;” Pali sajati “to let loose, send forth.”

In a calendar, having an extra day or month inserted.

Etymology (EN): O.E. hleapan “to jump, run, leap” (cf. O.S. hlopan, O.N. hlaupa, O.Fris. hlapa, Du. lopen, Ger. laufen “to run,” Goth. us-hlaupan “to jump up”), of uncertain origin, with no known cognates beyond Germanic. The noun is O.E. hlyp (Anglian *hlep). Noun in leap year, so called from its causing fixed festival days to “leap” ahead one day in the week.

Etymology (PE): Andarheli, from andarhel, verbal noun of andarhelidan, andarheštan “to insert,” from andar-→ inter- + helidan, heštan “to place, put” from Mid.Pers. hištan, hilidan “to let, set, leave, abandon;” Parthian Mid.Pers. hyrz; O.Pers. hard- “to send forth;” ava.hard- “to abandon;”
Av. harəz- “to discharge, send out; to filter,” hərəzaiti “releases, shoots;” cf. Skt. srj- “to let go or fly, throw, cast, emit, put forth;” Pali sajati “to let loose, send forth.”

The extra day added to a solar calendar (e.g. Gregorian, Iranian) in a leap year.

See also: → leap; → day.

The extra day added to a solar calendar (e.g. Gregorian, Iranian) in a leap year.

See also: → leap; → day.

An intercalary month employed in some calendars to preserve a seasonal relationship between the Lunar and Solar cycles. → embolismic month.

See also: → leap; → month.

An intercalary month employed in some calendars to preserve a seasonal relationship between the Lunar and Solar cycles. → embolismic month.

See also: → leap; → month.

A one-second added between 60s and 0s at announced times to keep the Coordinated Universal Time (UTC), counted by atomic clocks, within 0s.90 of mean solar time (UT1). Generally, leap seconds are added at the end of June or December.

See also: → leap; → second.

A one-second added between 60s and 0s at announced times to keep the Coordinated Universal Time (UTC), counted by atomic clocks, within 0s.90 of mean solar time (UT1). Generally, leap seconds are added at the end of June or December.

See also: → leap; → second.

In solar calendars the year that contains 366 days, instead of 365, in order to keep the calendar in pace with the real solar time.

See also: → leap; → year.

In solar calendars the year that contains 366 days, instead of 365, in order to keep the calendar in pace with the real solar time.

See also: → leap; → year.

The three criteria that identify → leap years in the → Gregorian calendar: 1)
The year must be evenly divisible by 4;

2. If the year can be evenly divided by 100, it is not a leap year, unless;

3. The year is also evenly divisible by 400.

This means that in the Gregorian calendar, the years 1600, 2000, and 2400 are leap years, while 1700, 1800, 1900, 2100, 2200, 2300 and 2500 are not leap years.

See also: → leap; → year; → rule.

The three criteria that identify → leap years in the → Gregorian calendar: 1)
The year must be evenly divisible by 4;

2. If the year can be evenly divided by 100, it is not a leap year, unless;

3. The year is also evenly divisible by 400.

This means that in the Gregorian calendar, the years 1600, 2000, and 2400 are leap years, while 1700, 1800, 1900, 2100, 2200, 2300 and 2500 are not leap years.

See also: → leap; → year; → rule.

Smallest in size, amount, degree, etc.

Etymology (EN): From M.E. leest(e), O.E. læst, læsest “smallest” (superlative of læs “smaller, less”).

Etymology (PE): Kucaktarin, kamtarin, superlatives of kucak and kam, → small.

Smallest in size, amount, degree, etc.

Etymology (EN): From M.E. leest(e), O.E. læst, læsest “smallest” (superlative of læs “smaller, less”).

Etymology (PE): Kucaktarin, kamtarin, superlatives of kucak and kam, → small.

Of two or more → integers, the smallest positive number that is divisible by those integers without a remainder.

See also: → least; → common; → multiplier.

Of two or more → integers, the smallest positive number that is divisible by those integers without a remainder.

See also: → least; → common; → multiplier.

Any statistical procedure that involves minimizing the sum of squared differences.

See also: → least; → square.

Any statistical procedure that involves minimizing the sum of squared differences.

See also: → least; → square.

A → cross correlation technique for computing average profiles from thousands of → spectral lines simultaneously. The technique, first introduced by Donati et al. (1997, MNRAS 291,658), is based on several assumptions: additive → line profiles, wavelength independent
→ limb darkening, self-similar local profile shape, and weak → magnetic fields. Thus, unpolarized/polarized stellar spectra can indeed be seen as a line pattern → convolved with an average line profile. In this context, extracting this average line profile amounts to a linear → deconvolution problem. The method treats it as a matrix problem and look for the → least squares solution. In practice, LSD is very similar to most other cross-correlation techniques, though slightly more sophisticated in the sense that it cleans the cross-correlation profile from the autocorrelation profile of the line pattern. The technique is used to investigate the physical processes that take place in stellar atmospheres and that affect all spectral line profiles in a similar way. This includes the study of line profile variations (LPV) caused by orbital motion of the star and/or stellar surface inhomogeneities, for example. However, its widest application nowadays is the detection of weak magnetic fields in stars over the entire → H-R diagram based on → Stokes parameter V (→ circular polarization) observations (see also Tkachenko et al., 2013, A&A 560, A37 and references therein).

See also: → least; → square; → deconvolution.

A → cross correlation technique for computing average profiles from thousands of → spectral lines simultaneously. The technique, first introduced by Donati et al. (1997, MNRAS 291,658), is based on several assumptions: additive → line profiles, wavelength independent
→ limb darkening, self-similar local profile shape, and weak → magnetic fields. Thus, unpolarized/polarized stellar spectra can indeed be seen as a line pattern → convolved with an average line profile. In this context, extracting this average line profile amounts to a linear → deconvolution problem. The method treats it as a matrix problem and look for the → least squares solution. In practice, LSD is very similar to most other cross-correlation techniques, though slightly more sophisticated in the sense that it cleans the cross-correlation profile from the autocorrelation profile of the line pattern. The technique is used to investigate the physical processes that take place in stellar atmospheres and that affect all spectral line profiles in a similar way. This includes the study of line profile variations (LPV) caused by orbital motion of the star and/or stellar surface inhomogeneities, for example. However, its widest application nowadays is the detection of weak magnetic fields in stars over the entire → H-R diagram based on → Stokes parameter V (→ circular polarization) observations (see also Tkachenko et al., 2013, A&A 560, A37 and references therein).

See also: → least; → square; → deconvolution.

A fit through data points using least squares.

See also: → least squares; → fit.

A fit through data points using least squares.

See also: → least squares; → fit.

1a) Go away from.

1b) To let remain or have remaining behind after going, disappearing, ceasing, etc.

2a) Permission to be absent, as from work or military duty.

2b) The time this permission lasts (Dictionary.com).

Etymology (EN): M.E. leven, from O.E. laefan “to allow to remain in the same state or condition” (cf. O.Saxon farlebid “left over;” Ger. bleiben “to remain”) ultimately from PIE *leip- “to stick, adhere;” also “fat,” from which the cognates: Gk. lipos “fat;” O.E. lifer “liver,” → life.

Etymology (PE): Parižidan, on the model of
Sariqoli barēzj “leavings;” Yaghnobi piraxs- “to stay behind, remain;” ultimately from Proto-Ir. *apa-raic-, from *raic- “to abandon, leave;” cf. Av. raēc- “to leave, let” (Cheung 2006), → heritage.

1a) Go away from.

1b) To let remain or have remaining behind after going, disappearing, ceasing, etc.

2a) Permission to be absent, as from work or military duty.

2b) The time this permission lasts (Dictionary.com).

Etymology (EN): M.E. leven, from O.E. laefan “to allow to remain in the same state or condition” (cf. O.Saxon farlebid “left over;” Ger. bleiben “to remain”) ultimately from PIE *leip- “to stick, adhere;” also “fat,” from which the cognates: Gk. lipos “fat;” O.E. lifer “liver,” → life.

Etymology (PE): Parižidan, on the model of
Sariqoli barēzj “leavings;” Yaghnobi piraxs- “to stay behind, remain;” ultimately from Proto-Ir. *apa-raic-, from *raic- “to abandon, leave;” cf. Av. raēc- “to leave, let” (Cheung 2006), → heritage.

Same as the → period-luminosity relation.

See also: Named after Henrietta Swan Leavitt (1868-1921), American woman astronomer, who discovered the relation between the luminosity and the period of → Cepheid variables (1912); → law.

Same as the → period-luminosity relation.

See also: Named after Henrietta Swan Leavitt (1868-1921), American woman astronomer, who discovered the relation between the luminosity and the period of → Cepheid variables (1912); → law.

A → primary cell in which the anode is a rod of carbon and the cathode a zinc rod both immersed in an electrolyte of ammonia plus a depolarizer.

See also: Named after the inventor Georges Leclanché (1839-1882), a French chemist, → cell.

A → primary cell in which the anode is a rod of carbon and the cathode a zinc rod both immersed in an electrolyte of ammonia plus a depolarizer.

See also: Named after the inventor Georges Leclanché (1839-1882), a French chemist, → cell.

1. The ninth of Jupiter’s known satellites and the smallest. It is 16 km in diameter and has its orbit at 11 million km from its planet. Also called Jupiter XIII, it was discovered by Charles Kowal (1940-), an American astronomer, in 1974.
   
2. An asteroid, 38 Leda, discovered by J. Chacornac in 1856.

See also: In Gk. mythology, Leda was queen of Sparta and the mother, by Zeus in the form of a swan, of Pollux and Helen of Troy.

1. The ninth of Jupiter’s known satellites and the smallest. It is 16 km in diameter and has its orbit at 11 million km from its planet. Also called Jupiter XIII, it was discovered by Charles Kowal (1940-), an American astronomer, in 1974.
   
2. An asteroid, 38 Leda, discovered by J. Chacornac in 1856.

See also: In Gk. mythology, Leda was queen of Sparta and the mother, by Zeus in the form of a swan, of Pollux and Helen of Troy.

An improvement of → Schwarzschild’s criterion for convective instability, which includes effects of chemical composition of the gas. In the Ledoux criterion the gradient due to different molecular weights is added to the adiabatic temperature gradient.

See also: After the Belgian astrophysicist Paul Ledoux (1914-1988), who studied problems of stellar stability and variable stars. He was awarded the Eddington Medal of the Royal Astronomical Society in 1972 (Ledoux et al. 1961 ApJ 133, 184); → criterion.

An improvement of → Schwarzschild’s criterion for convective instability, which includes effects of chemical composition of the gas. In the Ledoux criterion the gradient due to different molecular weights is added to the adiabatic temperature gradient.

See also: After the Belgian astrophysicist Paul Ledoux (1914-1988), who studied problems of stellar stability and variable stars. He was awarded the Eddington Medal of the Royal Astronomical Society in 1972 (Ledoux et al. 1961 ApJ 133, 184); → criterion.

Of, pertaining to, or located on or toward the west when somebody or something is facing north. Opposite of → right.

Etymology (EN): M.E. left, lift, luft, O.E. left, lyft- “weak, idle,” cf. Ger. link, Du. linker “left,” from O.H.G. slinc, M.Du. slink “left,” Swed. linka “limp,” slinka “dangle.”

Etymology (PE): Cap “left,” from unknown origin.

Of, pertaining to, or located on or toward the west when somebody or something is facing north. Opposite of → right.

Etymology (EN): M.E. left, lift, luft, O.E. left, lyft- “weak, idle,” cf. Ger. link, Du. linker “left,” from O.H.G. slinc, M.Du. slink “left,” Swed. linka “limp,” slinka “dangle.”

Etymology (PE): Cap “left,” from unknown origin.

See → Fleming’s rules.

See also: → left; → hand; → rule.

See → Fleming’s rules.

See also: → left; → hand; → rule.

Using the left hand with greater ease than the right.

Etymology (EN): → left; → hand + -ed.

Etymology (PE): Capâl, from cap, → left, + -al,
→ -al. Capdast, with dast, → hand.

Using the left hand with greater ease than the right.

Etymology (EN): → left; → hand + -ed.

Etymology (PE): Capâl, from cap, → left, + -al,
→ -al. Capdast, with dast, → hand.

1. The part of the body from the top of the → thigh down to the → foot.
   

   2. Anatomy: The lower limb of a human being between the → knee and the → ankle.

Etymology (EN): M.E., from O.Norse leggr; cognate with Dan. læg, Swed. läg “the calf of the leg.”

Etymology (PE): Leng, related to Mid.Pers. zang “shank, ankle;” Av. zanga-, zənga- “bone of the leg; ankle bone; ankle;” Skt. jánghā- “lower leg;” maybe somehow related to E. → shank.

1. The part of the body from the top of the → thigh down to the → foot.
   

   2. Anatomy: The lower limb of a human being between the → knee and the → ankle.

Etymology (EN): M.E., from O.Norse leggr; cognate with Dan. læg, Swed. läg “the calf of the leg.”

Etymology (PE): Leng, related to Mid.Pers. zang “shank, ankle;” Av. zanga-, zənga- “bone of the leg; ankle bone; ankle;” Skt. jánghā- “lower leg;” maybe somehow related to E. → shank.

1. Permitted by law; lawful.
   

2. Of or relating to law; connected with the law or its administration (Dictionary.com).

Etymology (EN): From M.Fr. légal or directly from L. legalis “legal, pertaining to the law,” from lex (genitive legis) “law.”

Etymology (PE): Qânuni, of or relating to qânun, → law.

1. Permitted by law; lawful.
   

2. Of or relating to law; connected with the law or its administration (Dictionary.com).

Etymology (EN): From M.Fr. légal or directly from L. legalis “legal, pertaining to the law,” from lex (genitive legis) “law.”

Etymology (PE): Qânuni, of or relating to qânun, → law.

1. A non-historical or unverifiable story handed down by tradition from earlier times and popularly accepted as historical.
   

2. The body of stories of this kind, especially as they relate to a particular people, group, or clan (Dictionary.com).

Etymology (EN): M.E. legende “written account of a saint’s life,”
from O.Fr. legende and directly from M.L. legenda literally, “(things) to be read,” noun use of feminine of L. legendus, gerund of legere “to read” (on certain days in church).

Etymology (PE): Cirok, from Kurd. cirok “story, fable,” related to Kurd. cir-, cirin “to sing, [to recite?];” Av. kar- “to celebrate, praise;” Proto-Ir. *karH- “to praise, celebrate;” cf. Skt. kar- “to celebrate, praise;” O.Norse herma “report;” O.Prussian kirdit “to hear;” PIE *kerH₂- “to celebrate” (Cheung 2007).

1. A non-historical or unverifiable story handed down by tradition from earlier times and popularly accepted as historical.
   

2. The body of stories of this kind, especially as they relate to a particular people, group, or clan (Dictionary.com).

Etymology (EN): M.E. legende “written account of a saint’s life,”
from O.Fr. legende and directly from M.L. legenda literally, “(things) to be read,” noun use of feminine of L. legendus, gerund of legere “to read” (on certain days in church).

Etymology (PE): Cirok, from Kurd. cirok “story, fable,” related to Kurd. cir-, cirin “to sing, [to recite?];” Av. kar- “to celebrate, praise;” Proto-Ir. *karH- “to praise, celebrate;” cf. Skt. kar- “to celebrate, praise;” O.Norse herma “report;” O.Prussian kirdit “to hear;” PIE *kerH₂- “to celebrate” (Cheung 2007).

Of, relating to, or of the nature of a legend.

See also: → legend; → -ary.

Of, relating to, or of the nature of a legend.

See also: → legend; → -ary.

The → differential equation of the form: d/dx(1 - x²)dy/dx) + n(n + 1)y = 0. The general solution of the Legendre equation is given by y = c₁P_n(x) + c₂Q_n(x), where P_n(x) are Legendre polynomials and Q_n(x) are called Legendre functions of the second kind.

See also: Named after Adrien-Marie Legendre (1752-1833),
a French mathematician who made important contributions to statistics, number theory, abstract algebra, and mathematical analysis; → equation.

The → differential equation of the form: d/dx(1 - x²)dy/dx) + n(n + 1)y = 0. The general solution of the Legendre equation is given by y = c₁P_n(x) + c₂Q_n(x), where P_n(x) are Legendre polynomials and Q_n(x) are called Legendre functions of the second kind.

See also: Named after Adrien-Marie Legendre (1752-1833),
a French mathematician who made important contributions to statistics, number theory, abstract algebra, and mathematical analysis; → equation.

A mathematical operation that transforms one function into another. Two differentiable functions f and g are said to be Legendre transforms of each other if their first derivatives are inverse functions of each other: df(x)/dx = (dg(x)/dx)^-1. The functions f and g are said to be related by a Legendre transformation.

See also: → Legendre equation; → transformation.

A mathematical operation that transforms one function into another. Two differentiable functions f and g are said to be Legendre transforms of each other if their first derivatives are inverse functions of each other: df(x)/dx = (dg(x)/dx)^-1. The functions f and g are said to be related by a Legendre transformation.

See also: → Legendre equation; → transformation.

1. The act of making or enacting laws.
   

2. A law or a body of laws enacted (Dictionary.com).

Etymology (EN): From Fr. législation, from L.L. legislationem, from legis latio, “proposing (literally ‘bearing’) of a law,” → legislator.

Etymology (PE): Qânungoz&acric;ri “act or process followed by the qânungoz&acric;r”, → legislator.

1. The act of making or enacting laws.
   

2. A law or a body of laws enacted (Dictionary.com).

Etymology (EN): From Fr. législation, from L.L. legislationem, from legis latio, “proposing (literally ‘bearing’) of a law,” → legislator.

Etymology (PE): Qânungoz&acric;ri “act or process followed by the qânungoz&acric;r”, → legislator.

1. A person who gives or makes laws.
   

2. A member of a legislative body (Dictionary.com).

Etymology (EN): From L. legis lator “proposer of a law,” from legis, genitive of lex, → law, + lator “proposer,” agent noun of latus “borne, brought, carried.”

Etymology (PE): Qânungozâr, literally “he who places the law,” from qânun, → law, + gozâr, present stem and agent noun of gozâštan “to place, put; perform; allow, permit,” related to gozaštan “to pass, to cross,” → trans-

1. A person who gives or makes laws.
   

2. A member of a legislative body (Dictionary.com).

Etymology (EN): From L. legis lator “proposer of a law,” from legis, genitive of lex, → law, + lator “proposer,” agent noun of latus “borne, brought, carried.”

Etymology (PE): Qânungozâr, literally “he who places the law,” from qânun, → law, + gozâr, present stem and agent noun of gozâštan “to place, put; perform; allow, permit,” related to gozaštan “to pass, to cross,” → trans-

A cosmological hypothesis, based on Einstein’s relativity, in which the expanding Universe began from an exploding “primeval atom.” In the Lemaître Universe the rate of expansion steadily decreases.

See also: Named after Monsignor Georges Edouard Lemaître (1894-1966), a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer; → universe.

A cosmological hypothesis, based on Einstein’s relativity, in which the expanding Universe began from an exploding “primeval atom.” In the Lemaître Universe the rate of expansion steadily decreases.

See also: Named after Monsignor Georges Edouard Lemaître (1894-1966), a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer; → universe.

1. A subsidiary proposition, proved for use in the proof of another proposition.
   

2. Linguistics: A word considered as its citation form together with all the → inflected forms. For example, the lemma go
   consists of go together with goes, going, went, and gone.
   

3. An argument or theme, especially when used as the subject or title of a composition (Dictionary.com).

Etymology (EN): From L. lemma, from Gk. lemma “something received or taken; an argument; something taken for granted,” from root of lambanein “to take,” → analemma.

Etymology (PE): Nehak, from neh present stem of nehâdan “to place, put; to set,” → position, + -ak a diminutive suffix of nouns.

1. A subsidiary proposition, proved for use in the proof of another proposition.
   

2. Linguistics: A word considered as its citation form together with all the → inflected forms. For example, the lemma go
   consists of go together with goes, going, went, and gone.
   

3. An argument or theme, especially when used as the subject or title of a composition (Dictionary.com).

Etymology (EN): From L. lemma, from Gk. lemma “something received or taken; an argument; something taken for granted,” from root of lambanein “to take,” → analemma.

Etymology (PE): Nehak, from neh present stem of nehâdan “to place, put; to set,” → position, + -ak a diminutive suffix of nouns.

A closed curve with two loops resembling a figure 8. It is represented by the Cartesian equation (x² + y²)² = a²(x² - y²), where a is the greatest distance from the origin (pole) to the curve. Its polar equation is r² = a² cos 2θ.

See also: From L. Latin lemniscatus “adorned with ribbons,” from lemniscus “a pendent ribbon,” from Gk. lemniskos “ribbon;” First described by Jacques Bernoulli (1654-1705) in 1694.

A closed curve with two loops resembling a figure 8. It is represented by the Cartesian equation (x² + y²)² = a²(x² - y²), where a is the greatest distance from the origin (pole) to the curve. Its polar equation is r² = a² cos 2θ.

See also: From L. Latin lemniscatus “adorned with ribbons,” from lemniscus “a pendent ribbon,” from Gk. lemniskos “ribbon;” First described by Jacques Bernoulli (1654-1705) in 1694.

A distance determined by the extent of something specified. → Jeans length

Etymology (EN): M.E. length(e), O.E. lengthu “length,” from P.Gmc. *langitho, noun of quality from *langgaz (root of O.E. lang “long,” cognate with Pers. derâz, as below) + -itho, abstract noun suffix. Cognate with O.N. lengd, O.Fris. lengethe, Du. lengte.

Etymology (PE): Derâzâ quality noun of derâz “long,” variants Laki, Kurdi derež;
Mid.Pers. drâz “long;” O.Pers. dargam “long;” Av. darəga-, darəγa- “long,” drājištəm “longest;” cf. Skt. dirghá- “lon (in space and time);” L. longus “long;” Gk. dolikhos “elongated;” O.H.G., Ger. lang; Goth. laggs “long;” PIE base *dlonghos- “long;” tul loan from Ar. ţaul, used in → wavelength.

A distance determined by the extent of something specified. → Jeans length

Etymology (EN): M.E. length(e), O.E. lengthu “length,” from P.Gmc. *langitho, noun of quality from *langgaz (root of O.E. lang “long,” cognate with Pers. derâz, as below) + -itho, abstract noun suffix. Cognate with O.N. lengd, O.Fris. lengethe, Du. lengte.

Etymology (PE): Derâzâ quality noun of derâz “long,” variants Laki, Kurdi derež;
Mid.Pers. drâz “long;” O.Pers. dargam “long;” Av. darəga-, darəγa- “long,” drājištəm “longest;” cf. Skt. dirghá- “lon (in space and time);” L. longus “long;” Gk. dolikhos “elongated;” O.H.G., Ger. lang; Goth. laggs “long;” PIE base *dlonghos- “long;” tul loan from Ar. ţaul, used in → wavelength.

Same as → Lorentz contraction.

See also: → length; → contraction.

Same as → Lorentz contraction.

See also: → length; → contraction.

1. Having or being of great length; very long.
   

2. Tediously verbose; very long; too long (Dictionary.com).

Etymology (EN): From → length + -y.

Etymology (PE): Kešnâk “lengthy” (Bardsiri, Kermâni), from kešidan, kašidan “to draw, protract, trail, drag, carry,” → tide. Bardesir, Kermân

1. Having or being of great length; very long.
   

2. Tediously verbose; very long; too long (Dictionary.com).

Etymology (EN): From → length + -y.

Etymology (PE): Kešnâk “lengthy” (Bardsiri, Kermâni), from kešidan, kašidan “to draw, protract, trail, drag, carry,” → tide. Bardesir, Kermân

A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually spherical) that they serve to converge or diverge the transmitted rays from an object, thus forming a real or virtual image of that object.

Etymology (EN): From L. lens (gen. lentis) “lentil,” cognate with Gk. lathyros, on analogy of the double-convex shape.

Etymology (PE): Adasi, related to adas “lentil,” from Ar. ‘adas.
The original Pers. terms for lentil are: mažu, mažâné, (Gilaki, Tabari) marju, marji, murje, marjum, (Laki) noži, (Aftari) marju, Mid.Pers. mijûg “lentil;” cf. Skt. masura- “lentil.”

A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually spherical) that they serve to converge or diverge the transmitted rays from an object, thus forming a real or virtual image of that object.

Etymology (EN): From L. lens (gen. lentis) “lentil,” cognate with Gk. lathyros, on analogy of the double-convex shape.

Etymology (PE): Adasi, related to adas “lentil,” from Ar. ‘adas.
The original Pers. terms for lentil are: mažu, mažâné, (Gilaki, Tabari) marju, marji, murje, marjum, (Laki) noži, (Aftari) marju, Mid.Pers. mijûg “lentil;” cf. Skt. masura- “lentil.”

→ optical system.

See also: → lens; → system.

→ optical system.

See also: → lens; → system.

An effect predicted by → general relativity whereby a rotating body alters the → space-time around it. This effect can be thought of as a kind of “dragging of inertial frames,” as first named by Einstein himself. A massive spinning object pulls nearby objects out of position compared to predictions for a non-rotating object.
The effect is important for rapidly rotating → neutron stars and → black holes, but that near Earth is extraordinarily small: 39 milli-arc second per year, about the width of a human hair seen from 400 meters away.

See also: Named after Austrian physicists Joseph Lense (1890-1985) and Hans Thirring (1888-1976), who first discovered this phenomenon in 1918; → effect.

An effect predicted by → general relativity whereby a rotating body alters the → space-time around it. This effect can be thought of as a kind of “dragging of inertial frames,” as first named by Einstein himself. A massive spinning object pulls nearby objects out of position compared to predictions for a non-rotating object.
The effect is important for rapidly rotating → neutron stars and → black holes, but that near Earth is extraordinarily small: 39 milli-arc second per year, about the width of a human hair seen from 400 meters away.

See also: Named after Austrian physicists Joseph Lense (1890-1985) and Hans Thirring (1888-1976), who first discovered this phenomenon in 1918; → effect.

1. The act or effect produced by a lens, in particular a → gravitational lens.
   
2. Pertaining to the object that produces the lensing effect. → lensing galaxy.

Etymology (EN): From → lens + → -ing.

Etymology (PE): 1) Lenzeš, verbal noun of lenzidan, verb formed from E. lens + -idan infinitive suffix.
2) Lenzandé, verbal adj. from lenzidan, as above.

1. The act or effect produced by a lens, in particular a → gravitational lens.
   
2. Pertaining to the object that produces the lensing effect. → lensing galaxy.

Etymology (EN): From → lens + → -ing.

Etymology (PE): 1) Lenzeš, verbal noun of lenzidan, verb formed from E. lens + -idan infinitive suffix.
2) Lenzandé, verbal adj. from lenzidan, as above.

Effect created by a → gravitational lens.

See also: → lensing; → effect.

Effect created by a → gravitational lens.

See also: → lensing; → effect.

A galaxy that acts as a → gravitational lens. The effect can also be due to a cluster of galaxies.

See also: → lensing; → galaxy.

A galaxy that acts as a → gravitational lens. The effect can also be due to a cluster of galaxies.

See also: → lensing; → galaxy.

An astronomical object that creates → gravitational lensing.
See also → lensing galaxy.

See also: → lensing; → object.

An astronomical object that creates → gravitational lensing.
See also → lensing galaxy.

See also: → lensing; → object.

An important quantity in the characterization of → gravitational lensing. The lensing potential is obtained by projecting the three-dimensional Newtonian potential on the lens plane and by properly re-scaling it. It is a two-dimensional analog to the → gravitational potential.

See also: → lensing; → potential.

An important quantity in the characterization of → gravitational lensing. The lensing potential is obtained by projecting the three-dimensional Newtonian potential on the lens plane and by properly re-scaling it. It is a two-dimensional analog to the → gravitational potential.

See also: → lensing; → potential.

Circular and elliptical features on the surface of → Europa with diameters ranging from 10 to 100 km. Many are domes that seem to have been pushed up from below. These domes might have been formed by warm water rising between the cold ices of the outer crust, in a scenario recalling the → magma chambers on Earth.

Etymology (EN): From L. lenticula “freckle,” diminutive of lens (genitive lentis) “lentil,” → lens.

Etymology (PE): Kakmak “freckle.”

Circular and elliptical features on the surface of → Europa with diameters ranging from 10 to 100 km. Many are domes that seem to have been pushed up from below. These domes might have been formed by warm water rising between the cold ices of the outer crust, in a scenario recalling the → magma chambers on Earth.

Etymology (EN): From L. lenticula “freckle,” diminutive of lens (genitive lentis) “lentil,” → lens.

Etymology (PE): Kakmak “freckle.”

A lens-shaped galaxy, which is an enormous grouping of old stars with very little internal structure.

See also: Lenticular “resembling a lentil in form,” → lens;
→ galaxy.

A lens-shaped galaxy, which is an enormous grouping of old stars with very little internal structure.

See also: Lenticular “resembling a lentil in form,” → lens;
→ galaxy.

The direction of an induced current is such as to oppose the cause producing it. The cause of the current may be the motion of a conductor in a magnetic field, or it may be the change of flux through a stationary circuit.

See also: Named after Heinrich Friedrich Emil Lenz (1804-1865), German physicist, who published the law in 1834; → law.

The direction of an induced current is such as to oppose the cause producing it. The cause of the current may be the motion of a conductor in a magnetic field, or it may be the change of flux through a stationary circuit.

See also: Named after Heinrich Friedrich Emil Lenz (1804-1865), German physicist, who published the law in 1834; → law.

The Lion. One of the most conspicuous → constellations in the northern hemisphere, at 10h 30m → right ascension, 15° north → declination. Leo is a constellation of the
→ Zodiac crossed by the Sun from August 10th to September 16th. Leo is visible from February through June. Its brightest star, α Leonis or → Regulus, is of the first magnitude.
Abbreviation: Leo; Genitive: Leonis.

The neighboring constellations are → Cancer, → Coma Berenices, → Crater, → Hydra, → Leo Minor, → Lynx, → Sextans, → Ursa Major, and → Virgo.

Leo contains many bright stars, many of which were individually identified by the ancients. There are four stars of first or second magnitude, which render this constellation especially prominent.

Apart from Regulus, the constellation is home to the bright stars → Denebola, the nearby star Wolf 359, and to a number of famous deep sky objects, among them galaxies Messier 65, Messier 66, Messier 95, Messier 96, Messier 105, and NGC 3628.

There are two → meteor showers associated with the constellation. The → Leonids usually peak on November 17-18 every year and have a → radiant near the bright star Gamma Leonis. The January Leonids are a minor shower that peaks between January 1 and 7. Leo has 11 stars with known planets.

See also: → lion.

The Lion. One of the most conspicuous → constellations in the northern hemisphere, at 10h 30m → right ascension, 15° north → declination. Leo is a constellation of the
→ Zodiac crossed by the Sun from August 10th to September 16th. Leo is visible from February through June. Its brightest star, α Leonis or → Regulus, is of the first magnitude.
Abbreviation: Leo; Genitive: Leonis.

The neighboring constellations are → Cancer, → Coma Berenices, → Crater, → Hydra, → Leo Minor, → Lynx, → Sextans, → Ursa Major, and → Virgo.

Leo contains many bright stars, many of which were individually identified by the ancients. There are four stars of first or second magnitude, which render this constellation especially prominent.

Apart from Regulus, the constellation is home to the bright stars → Denebola, the nearby star Wolf 359, and to a number of famous deep sky objects, among them galaxies Messier 65, Messier 66, Messier 95, Messier 96, Messier 105, and NGC 3628.

There are two → meteor showers associated with the constellation. The → Leonids usually peak on November 17-18 every year and have a → radiant near the bright star Gamma Leonis. The January Leonids are a minor shower that peaks between January 1 and 7. Leo has 11 stars with known planets.

See also: → lion.

The Lesser Lion. A faint constellation in the northern hemisphere, at 10h 20m right ascension, 35° north declination.
Abbreviation: LMi; genitive: Leonis Minoris.

Etymology (EN): → Leo; Minor, from L. minor “lesser, smaller, junior,” from PIE base *min- “small.”

Etymology (PE): Šir, → Leo; kucak “small,” (Mid.Pers. kucak “small”), related to kutâh “short, small, little,” kudak “child, infant,” kutulé, → dwarf, Mid.Pers. kôtâh “low,” kôtak “small, young; baby;” Av. kutaka- “little, small.”

The Lesser Lion. A faint constellation in the northern hemisphere, at 10h 20m right ascension, 35° north declination.
Abbreviation: LMi; genitive: Leonis Minoris.

Etymology (EN): → Leo; Minor, from L. minor “lesser, smaller, junior,” from PIE base *min- “small.”

Etymology (PE): Šir, → Leo; kucak “small,” (Mid.Pers. kucak “small”), related to kutâh “short, small, little,” kudak “child, infant,” kutulé, → dwarf, Mid.Pers. kôtâh “low,” kôtak “small, young; baby;” Av. kutaka- “little, small.”

A → dwarf galaxy recently discovered near the Milky Way in
→ neutral hydrogen → 21-centimeter line observations. Optical imaging observations indicate that
it is located between 1.5 and 2.0 Mpc from the Milky Way. This places Leo P in the → Local Volume but beyond the → Local Group. The dwarf galaxy has extreme properties: it is the lowest-mass system known that contains significant amounts of gas and is
currently forming stars (Katherine L. Rhode et al. 2013, AJ 145, 149).

See also: → Leo.

A → dwarf galaxy recently discovered near the Milky Way in
→ neutral hydrogen → 21-centimeter line observations. Optical imaging observations indicate that
it is located between 1.5 and 2.0 Mpc from the Milky Way. This places Leo P in the → Local Volume but beyond the → Local Group. The dwarf galaxy has extreme properties: it is the lowest-mass system known that contains significant amounts of gas and is
currently forming stars (Katherine L. Rhode et al. 2013, AJ 145, 149).

See also: → Leo.

A → meteor shower emanating from an apparent point in the constellation → Leo that occurs from November 14-20, with a maximum on November 17-18. It is due to the annual passage of the Earth through the orbit of the comet → Tempel-Tuttle and encounter with the dust debris from the comet.

See also: From L. Leon, → Leo, + → -ids.

A → meteor shower emanating from an apparent point in the constellation → Leo that occurs from November 14-20, with a maximum on November 17-18. It is due to the annual passage of the Earth through the orbit of the comet → Tempel-Tuttle and encounter with the dust debris from the comet.

See also: From L. Leon, → Leo, + → -ids.

A frequency distribution with a positive → kurtosis, that has a more elevated peak around the mean than the corresponding normal distribution.
→ platykurtic.

Etymology (EN): From Gk. lepto-, combining form of leptos “thin, slight”

• → kurtosis.

Etymology (PE): Boland-afrâšté “highly-elevated,” from boland “high, tall, elevated, sublime” (variants bâlâ “up, above, high, elevated, height,” borz “height, magnitude” (it occurs also in the name of the mountain chain Alborz),
Laki dialect berg “hill, mountain;”
Mid.Pers. buland “high;” O.Pers. baršan- “height;” Av. barəz- “high, mount,” barezan- “height;” cf. Skt. bhrant- “high;” L. fortis “strong” (Fr. and E. force); O.E. burg, burh “castle, fortified place,” from P.Gmc. *burgs “fortress;” Ger. Burg “castle,” Goth. baurgs “city,” E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- “high”) + afrâšté “raised, elevated, erect,” p.p. of afrâštan,
→ kurtosis.

A frequency distribution with a positive → kurtosis, that has a more elevated peak around the mean than the corresponding normal distribution.
→ platykurtic.

Etymology (EN): From Gk. lepto-, combining form of leptos “thin, slight”

• → kurtosis.

Etymology (PE): Boland-afrâšté “highly-elevated,” from boland “high, tall, elevated, sublime” (variants bâlâ “up, above, high, elevated, height,” borz “height, magnitude” (it occurs also in the name of the mountain chain Alborz),
Laki dialect berg “hill, mountain;”
Mid.Pers. buland “high;” O.Pers. baršan- “height;” Av. barəz- “high, mount,” barezan- “height;” cf. Skt. bhrant- “high;” L. fortis “strong” (Fr. and E. force); O.E. burg, burh “castle, fortified place,” from P.Gmc. *burgs “fortress;” Ger. Burg “castle,” Goth. baurgs “city,” E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- “high”) + afrâšté “raised, elevated, erect,” p.p. of afrâštan,
→ kurtosis.

An → elementary particle that does not participate in the → strong interaction. The Lepton family
includes → electrons, → muons, tau leptons, → neutrinos and their → antiparticles. The lepton is a
→ fermion.

See also: From Gk, lepto-, combining form of leptos “small, slight” + -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon; graviton), and other minimal entities or components.

An → elementary particle that does not participate in the → strong interaction. The Lepton family
includes → electrons, → muons, tau leptons, → neutrinos and their → antiparticles. The lepton is a
→ fermion.

See also: From Gk, lepto-, combining form of leptos “small, slight” + -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon; graviton), and other minimal entities or components.

Postulate that the magnitude of the lepton number density is comparable to or larger than the thermal radiation photon number density, so relaxation to equilibrium produces a degenerate sea of neutrinos. Degenerate neutrinos would suppress the number of neutrons relative to protons in the very early Universe; degenerate antineutrinos would suppress the number of protons relative to neutrons. Either case would affect BBNS (Peebles, P. et al., 2009, Finding the Big Bang, Cambridge: UK, Cambridge Univ. Press).

See also: → lepton; → degeneracy.

Postulate that the magnitude of the lepton number density is comparable to or larger than the thermal radiation photon number density, so relaxation to equilibrium produces a degenerate sea of neutrinos. Degenerate neutrinos would suppress the number of neutrons relative to protons in the very early Universe; degenerate antineutrinos would suppress the number of protons relative to neutrons. Either case would affect BBNS (Peebles, P. et al., 2009, Finding the Big Bang, Cambridge: UK, Cambridge Univ. Press).

See also: → lepton; → degeneracy.

The era following the hadronic era, when the Universe consisted mainly of leptons and photons. It began when the temperature dropped below 10¹² degrees kelvin some 10^-4 seconds after the Big Bang, and it lasted until the temperature fell below 10¹⁰ degrees kelvin, at an era of about 1 second.

See also: → lepton; → era.

The era following the hadronic era, when the Universe consisted mainly of leptons and photons. It began when the temperature dropped below 10¹² degrees kelvin some 10^-4 seconds after the Big Bang, and it lasted until the temperature fell below 10¹⁰ degrees kelvin, at an era of about 1 second.

See also: → lepton; → era.

In particle physics, a quantum number attributed to elementary particles which is conserved in nuclear reactions. It is +1 for a lepton, -1 for an antilepton and 0 for other particles.

See also: → lepton; → number.

In particle physics, a quantum number attributed to elementary particles which is conserved in nuclear reactions. It is +1 for a lepton, -1 for an antilepton and 0 for other particles.

See also: → lepton; → number.

The Hare. A small → constellation in the southern hemisphere at about 6h right ascension, 20° south declination. Abbreviation: Lep; genitive: Leporis.

Etymology (EN): L. lepus “hare.”

Etymology (PE): Xarguš “rabbit, hare,” literally “ass-ear,” Mid.Pers. xargôš, from xar “donkey, ass” (Mid.Pers. xar “donkey;” Av. xara- “donkey;” cf. Skt. khára- “donkey, mule”)

• guš, → ear.

The Hare. A small → constellation in the southern hemisphere at about 6h right ascension, 20° south declination. Abbreviation: Lep; genitive: Leporis.

Etymology (EN): L. lepus “hare.”

Etymology (PE): Xarguš “rabbit, hare,” literally “ass-ear,” Mid.Pers. xargôš, from xar “donkey, ass” (Mid.Pers. xar “donkey;” Av. xara- “donkey;” cf. Skt. khára- “donkey, mule”)

• guš, → ear.

A bright blue star of → apparent visual magnitudeV = 2.70, that with → Shaula (Lambda Scorpii) makes up the Scorpion’s stinger. Among its other designations: HR 6508 and HIP 85696. Lesath is 580 → light-years away.

Lesath and Shaula appear very close on the sky (less than a degree apart), but they are not physically related. Lesath is a → subgiant of → spectral type B2 IV with a → luminosity of about 7,380 Msun. It has a radius of about 6 Rsun, and a → surface temperature of about 22,000 K.

See also: Lesath, from Ar. al-Las’ah (اللسعه) “the sting.”

A bright blue star of → apparent visual magnitudeV = 2.70, that with → Shaula (Lambda Scorpii) makes up the Scorpion’s stinger. Among its other designations: HR 6508 and HIP 85696. Lesath is 580 → light-years away.

Lesath and Shaula appear very close on the sky (less than a degree apart), but they are not physically related. Lesath is a → subgiant of → spectral type B2 IV with a → luminosity of about 7,380 Msun. It has a radius of about 6 Rsun, and a → surface temperature of about 22,000 K.

See also: Lesath, from Ar. al-Las’ah (اللسعه) “the sting.”

1. A symbol or character representing a sound of which words are formed used in writing and printing a language.
   

2. A written or printed communication addressed to a person or organization.

Etymology (EN): M.E., from O.Fr. letre “character, letter; missive,” from L. littera “letter of the alphabet,” litterae (plural) “epistle, literature”

Etymology (PE): 1) Vât “letter, word,” from vat- “to speak, say;” cf. (Kurd.) wittin “to speak, say,” → article,
(Nâyin) vâte, (Qohrud) vâta, (Sangesar) -vât-/vân, (Zazaki) vâtiš, (Awromani) wâtay/wâc-, (Farizand) -vât/-vaj, (Gaz) vâ-/vât, related to Pers. vâžé “word;” Mid.Pers. vâc, vâcak “word, speech;” âva “voice, sound,” âvâz “voice, sound, song,” bâng “voice, sound, clamour” (Mid.Pers. vâng); Av. vacah- “word,” vaocanghê “to decalre” (by means of speech), from vac- “to speak, say;” cf. Skt. vakti “speaks, says,” vacas- “word;”
Gk. epos “word;” L. vox “voice;” PIE base *wek- “to speak.”

2. Nâmé, → book.

1. A symbol or character representing a sound of which words are formed used in writing and printing a language.
   

2. A written or printed communication addressed to a person or organization.

Etymology (EN): M.E., from O.Fr. letre “character, letter; missive,” from L. littera “letter of the alphabet,” litterae (plural) “epistle, literature”

Etymology (PE): 1) Vât “letter, word,” from vat- “to speak, say;” cf. (Kurd.) wittin “to speak, say,” → article,
(Nâyin) vâte, (Qohrud) vâta, (Sangesar) -vât-/vân, (Zazaki) vâtiš, (Awromani) wâtay/wâc-, (Farizand) -vât/-vaj, (Gaz) vâ-/vât, related to Pers. vâžé “word;” Mid.Pers. vâc, vâcak “word, speech;” âva “voice, sound,” âvâz “voice, sound, song,” bâng “voice, sound, clamour” (Mid.Pers. vâng); Av. vacah- “word,” vaocanghê “to decalre” (by means of speech), from vac- “to speak, say;” cf. Skt. vakti “speaks, says,” vacas- “word;”
Gk. epos “word;” L. vox “voice;” PIE base *wek- “to speak.”

2. Nâmé, → book.

A position with respect to a given or specified base. → energy level.

Etymology (EN): From O.Fr. livel, from L. libella “a balance, level,” diminutive of libra “balance, scale.”

Etymology (PE): Tarâz “level; a level,” from tarâzu “balance, scales,” Mid.Pers. tarâzên-, taraênidan “to weigh,” Proto-Iranian *tarāz-, from *tarā- “balance, scale” ( cf. Skt. tulā- “scales, balance, weight,” from tul- “to weigh, make equal in weight, equal,” tolayati “weighs, balances,” L. tollere “to raise,”
Gk. talanton “balance, weight,” Atlas “the Bearer” of Heaven," Lith. tiltas “bridge;” PIE base telə- “to lift, weigh”) + Av. az- “to convey, conduct, drive,” azaiti drives" (cf. Skt. aj- “to dive, sling,” ájati “drives,” ajirá- “agile, quick,”
Gk. agein “to lead, guide, drive, carry off,” L. agere “to do, set in motion, drive,” from PIE root *ag- “to drive, move,” → act).

A position with respect to a given or specified base. → energy level.

Etymology (EN): From O.Fr. livel, from L. libella “a balance, level,” diminutive of libra “balance, scale.”

Etymology (PE): Tarâz “level; a level,” from tarâzu “balance, scales,” Mid.Pers. tarâzên-, taraênidan “to weigh,” Proto-Iranian *tarāz-, from *tarā- “balance, scale” ( cf. Skt. tulā- “scales, balance, weight,” from tul- “to weigh, make equal in weight, equal,” tolayati “weighs, balances,” L. tollere “to raise,”
Gk. talanton “balance, weight,” Atlas “the Bearer” of Heaven," Lith. tiltas “bridge;” PIE base telə- “to lift, weigh”) + Av. az- “to convey, conduct, drive,” azaiti drives" (cf. Skt. aj- “to dive, sling,” ájati “drives,” ajirá- “agile, quick,”
Gk. agein “to lead, guide, drive, carry off,” L. agere “to do, set in motion, drive,” from PIE root *ag- “to drive, move,” → act).

Same as → significance level.

See also: → level; → significance.

Same as → significance level.

See also: → level; → significance.

A rigid bar that pivots about a point and is used to move or lift a load at one end by applying force to the other end. → lever arm.

Etymology (EN): M.E. levere, levour; O.Fr. levier “a lifter, a lever,” agent noun from lever “to raise,” from L. levare “to raise,” from levis “light” in weight.

Etymology (PE): Ahrom, of unknown etymology.

A rigid bar that pivots about a point and is used to move or lift a load at one end by applying force to the other end. → lever arm.

Etymology (EN): M.E. levere, levour; O.Fr. levier “a lifter, a lever,” agent noun from lever “to raise,” from L. levare “to raise,” from levis “light” in weight.

Etymology (PE): Ahrom, of unknown etymology.

The distance between the point of application of a → force and the → axis around which the object could
→ rotate.

See also: → lever; → arm.

The distance between the point of application of a → force and the → axis around which the object could
→ rotate.

See also: → lever; → arm.

1. To rise or float in the air, especially by means of supposed magical powers.
   

   2. To cause to rise or float in the air.

Etymology (EN): From L. levitas “lightness,” from levis “light.”

Etymology (PE): Bâlâ kardan, literally “to raise, uplift,” from bâlâ “high, up,” → high, + kardan “to do, perform, make,” → effect; bâlâ šodan, from bâlâ + šodan “to go, to pass, to become,” → set.

1. To rise or float in the air, especially by means of supposed magical powers.
   

   2. To cause to rise or float in the air.

Etymology (EN): From L. levitas “lightness,” from levis “light.”

Etymology (PE): Bâlâ kardan, literally “to raise, uplift,” from bâlâ “high, up,” → high, + kardan “to do, perform, make,” → effect; bâlâ šodan, from bâlâ + šodan “to go, to pass, to become,” → set.

1. The action of rising or causing something to rise and float in the air, typically by means of supposed magical powers.
   

   2. → radiative levitation.

See also: → levitate; → -tion.

1. The action of rising or causing something to rise and float in the air, typically by means of supposed magical powers.
   

   2. → radiative levitation.

See also: → levitate; → -tion.

A combining form meaning “left” and “counterclockwise,” used in the formation of compound words, such as → levorotation, levocardia, levoglucose, etc. The variant lev- occurs before vowels. Compare → dextro-.

Etymology (EN): From L. laevo-, from laevus, cf. Gk. laios, Russ. levyj,

• epenthetic vowel -o-.

Etymology (PE): Cap-, from cap “left,” of unknown etymology.

A combining form meaning “left” and “counterclockwise,” used in the formation of compound words, such as → levorotation, levocardia, levoglucose, etc. The variant lev- occurs before vowels. Compare → dextro-.

Etymology (EN): From L. laevo-, from laevus, cf. Gk. laios, Russ. levyj,

• epenthetic vowel -o-.

Etymology (PE): Cap-, from cap “left,” of unknown etymology.

The counterclockwise rotation of the → plane of polarization of light (as observed when looking straight through the incoming light) by certain substances.

See also: Adj. related to → levorotation.

The counterclockwise rotation of the → plane of polarization of light (as observed when looking straight through the incoming light) by certain substances.

See also: Adj. related to → levorotation.

Relating to an → optically active substance that brings about → levorotation.

See also: Adj. related to → levorotation.

Relating to an → optically active substance that brings about → levorotation.

See also: Adj. related to → levorotation.

A branch of → linguistics that deals with the principle and methods of writing dictionaries.

See also: → lexicology; → -graphy.

A branch of → linguistics that deals with the principle and methods of writing dictionaries.

See also: → lexicology; → -graphy.

A branch of → linguistics that studies the formation, meaning, and use of words and their idiomatic combinations. In contrast to → terminology, lexicology is based on words and does not conceive of meaning unless it is related to the word.

Etymology (EN): From lexic, from Gk. lexicon, noun use of lexikos “pertaining to words,” from lexis “word; speech” (+ -ikos, → -ics), from legein “to say, speak, recount,”

• -o-, + → -logy.

Etymology (PE): Vâžešnâsi, from vâžé, → word,

• -šenâsi, → -logy.

A branch of → linguistics that studies the formation, meaning, and use of words and their idiomatic combinations. In contrast to → terminology, lexicology is based on words and does not conceive of meaning unless it is related to the word.

Etymology (EN): From lexic, from Gk. lexicon, noun use of lexikos “pertaining to words,” from lexis “word; speech” (+ -ikos, → -ics), from legein “to say, speak, recount,”

• -o-, + → -logy.

Etymology (PE): Vâžešnâsi, from vâžé, → word,

• -šenâsi, → -logy.

An early form of → capacitors which is a glass jar coated inside and outside about half way up the side with metal foil. A chain connects the inner coating to a rod which usually terminates in a small brass knob. The jar is charged by connecting the knob, that is the inner metal coating, to a charged body, meanwhile grounding the outer coating. Same as Leiden jar

Etymology (EN): Named after Leyden (Leiden) the city where it was invented by the Dutch scientist Pieter van Musschenbroek in 1745,
independently from the German Ewald Georg von Kleist; jar a usually “cylindrical vessel,” from M.Fr. jarre, from Provençal jarra, from Ar. jarrah.

Etymology (PE): Botri, → bottle.

An early form of → capacitors which is a glass jar coated inside and outside about half way up the side with metal foil. A chain connects the inner coating to a rod which usually terminates in a small brass knob. The jar is charged by connecting the knob, that is the inner metal coating, to a charged body, meanwhile grounding the outer coating. Same as Leiden jar

Etymology (EN): Named after Leyden (Leiden) the city where it was invented by the Dutch scientist Pieter van Musschenbroek in 1745,
independently from the German Ewald Georg von Kleist; jar a usually “cylindrical vessel,” from M.Fr. jarre, from Provençal jarra, from Ar. jarrah.

Etymology (PE): Botri, → bottle.