An Etymological Dictionary of Astronomy and Astrophysics

Not powerful or intense.
→ electroweak epoch, → electroweak force, → electroweak interaction, → weak anthropic principle, → weak arm spiral galaxy, → weak emission-line central star, → weak encounter, → weak equivalence principle, → weak force, → weak gravitational lensing, → weak interaction, → weak lensing, → weak nuclear force, → weak wind problem, → weak-line T Tauri star, → weak-wind O-type star.

Etymology (EN): From O.N. veikr “weak,” cognate with O.E. wac “weak, pliant, soft,” from P.Gmc. *waikwaz “yield,” *wikanan “bend” (cf. Du. week “weak, soft, tender,” O.H.G. weih “yielding, soft,” Ger. weich “soft,” from PIE base *weik- “to bend, wind”

Etymology (PE): Nezâr “weak, feeble, thin, slim; flesh without fat” (bâde-ye nezâr “a wine with minute alcohol,” soxan-e nezâr “inconsistent, weak statement”), variant zâr, Mid.Pers. nizâr (prefixed *ni- + *zâr/*zar) “weak, feeble,” Mid./Mod.Pers. zarmân “old man, deterioration,” Av. zairina- “exhausting, slackening,” zaurura- “weak through old age, decrepit,” cf. Skt. jára- “wearing out, exhaustion,” jaranā- “old, decayed,” jarimán- “weakness through old age,” Gk. geron “old man,” L. granum “grain;” PIE base *ger- “wear away.”
Tâm, → faint.
Sost, from Mid.Pers. sust “weak, lazy.”
Kamnur, from kam “little, few; deficient, wanting; scarce”
(Mid.Pers. kam “little, small, few,” O.Pers./Av. kamna- “small, few”)

• nur, → light.
  Kamzur, from ham + zur, → strength.

Not powerful or intense.
→ electroweak epoch, → electroweak force, → electroweak interaction, → weak anthropic principle, → weak arm spiral galaxy, → weak emission-line central star, → weak encounter, → weak equivalence principle, → weak force, → weak gravitational lensing, → weak interaction, → weak lensing, → weak nuclear force, → weak wind problem, → weak-line T Tauri star, → weak-wind O-type star.

Etymology (EN): From O.N. veikr “weak,” cognate with O.E. wac “weak, pliant, soft,” from P.Gmc. *waikwaz “yield,” *wikanan “bend” (cf. Du. week “weak, soft, tender,” O.H.G. weih “yielding, soft,” Ger. weich “soft,” from PIE base *weik- “to bend, wind”

Etymology (PE): Nezâr “weak, feeble, thin, slim; flesh without fat” (bâde-ye nezâr “a wine with minute alcohol,” soxan-e nezâr “inconsistent, weak statement”), variant zâr, Mid.Pers. nizâr (prefixed *ni- + *zâr/*zar) “weak, feeble,” Mid./Mod.Pers. zarmân “old man, deterioration,” Av. zairina- “exhausting, slackening,” zaurura- “weak through old age, decrepit,” cf. Skt. jára- “wearing out, exhaustion,” jaranā- “old, decayed,” jarimán- “weakness through old age,” Gk. geron “old man,” L. granum “grain;” PIE base *ger- “wear away.”
Tâm, → faint.
Sost, from Mid.Pers. sust “weak, lazy.”
Kamnur, from kam “little, few; deficient, wanting; scarce”
(Mid.Pers. kam “little, small, few,” O.Pers./Av. kamna- “small, few”)

• nur, → light.
  Kamzur, from ham + zur, → strength.

A version of the → anthropic principle whereby the initial conditions in the → Universe are → constrained by the fact that → intelligent life has appeared.

See also: → weak; → anthropic; → principle.

A version of the → anthropic principle whereby the initial conditions in the → Universe are → constrained by the fact that → intelligent life has appeared.

See also: → weak; → anthropic; → principle.

A gas-rich galaxy that has weak stellar → spiral arms with → interarm gas and star formation more important than a typical → spiral galaxy, such as NGC 4414.

See also: → weak; → arm; → spiral; → galaxy.

A gas-rich galaxy that has weak stellar → spiral arms with → interarm gas and star formation more important than a typical → spiral galaxy, such as NGC 4414.

See also: → weak; → arm; → spiral; → galaxy.

A member of a class of cntral stars of planetary nebula, → CSPN, which have weaker and narrower emission lines than → Wolf-Rayet-like CSPNe (Tylenda et al. 1993, A&AS 102, 595).

See also: → weak; → emission; → line.

A member of a class of cntral stars of planetary nebula, → CSPN, which have weaker and narrower emission lines than → Wolf-Rayet-like CSPNe (Tylenda et al. 1993, A&AS 102, 595).

See also: → weak; → emission; → line.

In a → star cluster, an → encounter that occurs at a distance and produces only very small changes in a star’s velocity.

See also: → weak; → encounter.

In a → star cluster, an → encounter that occurs at a distance and produces only very small changes in a star’s velocity.

See also: → weak; → encounter.

All structureless bodies fall along the same → path in a → gravitational field, independent of their composition. Also known as → universality of free fall. See also: → equivalence principle, → Einstein equivalence principle.

See also: → weak; → equivalence; → principle.

All structureless bodies fall along the same → path in a → gravitational field, independent of their composition. Also known as → universality of free fall. See also: → equivalence principle, → Einstein equivalence principle.

See also: → weak; → equivalence; → principle.

Same as → weak interaction.

See also: → weak; → force.

Same as → weak interaction.

See also: → weak; → force.

A gravitational bending of light by structures in the Universe that distorts the images of distant galaxies. The distortion allows the distribution of → dark matter and its evolution with time to be measured, thereby probing the influence of → dark energy on the growth of structures. Weak gravitational lensing is generally difficult to identify in individual images, in contrast to → strong gravitational lensing (see, e.g., Bartelmann & Peter Schneider, 2001, Phys. Rept. 340, 291).

See also: → weak; → gravitational; → lensing.

A gravitational bending of light by structures in the Universe that distorts the images of distant galaxies. The distortion allows the distribution of → dark matter and its evolution with time to be measured, thereby probing the influence of → dark energy on the growth of structures. Weak gravitational lensing is generally difficult to identify in individual images, in contrast to → strong gravitational lensing (see, e.g., Bartelmann & Peter Schneider, 2001, Phys. Rept. 340, 291).

See also: → weak; → gravitational; → lensing.

One of the fundamental forces of nature that accounts for some particle interaction, such as → beta decay (→ radioactivity), the decay of free → neutrons, → neutrino interactions, and so forth. It is short-ranged, dominating at distances of 10^-16 cm and occurs at a rate slower than that of the → strong interaction by a factor of about 10^-13, hence its name. Although the weak interaction also includes interactions in which no neutrinos are emitted, neutrino emission accompanies all weak interactions of interest to astrophysics. Weak interaction plays an important role in the evolution of the stars from birth to death. For example, the → proton-proton reaction is a weak interaction. Also called → weak force or → weak nuclear force.

See also: → weak; → interaction.

One of the fundamental forces of nature that accounts for some particle interaction, such as → beta decay (→ radioactivity), the decay of free → neutrons, → neutrino interactions, and so forth. It is short-ranged, dominating at distances of 10^-16 cm and occurs at a rate slower than that of the → strong interaction by a factor of about 10^-13, hence its name. Although the weak interaction also includes interactions in which no neutrinos are emitted, neutrino emission accompanies all weak interactions of interest to astrophysics. Weak interaction plays an important role in the evolution of the stars from birth to death. For example, the → proton-proton reaction is a weak interaction. Also called → weak force or → weak nuclear force.

See also: → weak; → interaction.

The → gravitational lensing in which the images are only weakly distorted, and do not form wide arcs or multiple image systems. This happens if the → gravitational lens mass in front of a source is not concentrated enough to form multiple images. The resulting small distortions cannot be seen on individual sources, as we do not know their unlensed, “intrinsic” shape. However, if an entire population of background sources is available, the distortions can be revealed, either statistically or by local averaging. See also → strong lensing.

See also: → weak; → lensing.

The → gravitational lensing in which the images are only weakly distorted, and do not form wide arcs or multiple image systems. This happens if the → gravitational lens mass in front of a source is not concentrated enough to form multiple images. The resulting small distortions cannot be seen on individual sources, as we do not know their unlensed, “intrinsic” shape. However, if an entire population of background sources is available, the distortions can be revealed, either statistically or by local averaging. See also → strong lensing.

See also: → weak; → lensing.

Same as → weak interaction.

See also: → weak; → nuclear; → force.

Same as → weak interaction.

See also: → weak; → nuclear; → force.

The discrepancy between the observed → mass loss rates and the predicted values for → weak-wind O-type stars.

See also: → weak; → wind; → problem.

The discrepancy between the observed → mass loss rates and the predicted values for → weak-wind O-type stars.

See also: → weak; → wind; → problem.

A T Tauri star that lacks strong emission lines in its optical spectrum, and lacks both strong → stellar wind and → infrared excess. These objects are believed to be → pre-main sequence stars
without obvious signs for disk → accretion. Weak-line T Tauri stars result from the evolution of → classical T Tauri stars.

See also: → weak; → line; → T Tauri star.

A T Tauri star that lacks strong emission lines in its optical spectrum, and lacks both strong → stellar wind and → infrared excess. These objects are believed to be → pre-main sequence stars
without obvious signs for disk → accretion. Weak-line T Tauri stars result from the evolution of → classical T Tauri stars.

See also: → weak; → line; → T Tauri star.

A → main sequence → O star with low luminosity and surprisingly weak → stellar wind compared to “classical” dwarfs. The → mass loss rates are lower than 10^-8 solar masses per year and the → modified wind momenta nearly 2 orders of magnitude smaller than that expected from wind models for typical O stars. Weak-wind O-type stars occur in both → metal-rich and → metal-poor environments. Their nature is not yet fully understood. same as → weak wind problem.

See also: → weak; → wind; → O-type star.

A → main sequence → O star with low luminosity and surprisingly weak → stellar wind compared to “classical” dwarfs. The → mass loss rates are lower than 10^-8 solar masses per year and the → modified wind momenta nearly 2 orders of magnitude smaller than that expected from wind models for typical O stars. Weak-wind O-type stars occur in both → metal-rich and → metal-poor environments. Their nature is not yet fully understood. same as → weak wind problem.

See also: → weak; → wind; → O-type star.

The state of the → atmosphere, mainly with regard to its effects of temperature, cloudiness, rainfall, wind, etc. upon life and human activities. As distinguished from → climate, weather consists of the short-term variations in the atmosphere.

Etymology (EN): M.E., from O.E. weder; cf. M.Du., Du. weder, O.H.G. wetar, Ger. Wetter “storm, wind, weather.”

Etymology (PE): Havâb, short for havâ “weather; air” (see below) + âb→ water, from âb o havâ “weather; climate.”
Havâ, from Ar., probably itself a loanword from Mid.Pers. vây “weather, air,” Av. vayah-, vaya- “weather,” from va- “to blow;” cf. Skt. va-, Gk. aemi- “to blow;” Av. vâta- “wind,” Skt. vata-,
L. ventus, Mod. Pers. bâd “wind.” PIE *we- “to blow;” havâb contraction of havâ + âb “→ water,” from âb o havâ “weather,” literally “water and air.”

The state of the → atmosphere, mainly with regard to its effects of temperature, cloudiness, rainfall, wind, etc. upon life and human activities. As distinguished from → climate, weather consists of the short-term variations in the atmosphere.

Etymology (EN): M.E., from O.E. weder; cf. M.Du., Du. weder, O.H.G. wetar, Ger. Wetter “storm, wind, weather.”

Etymology (PE): Havâb, short for havâ “weather; air” (see below) + âb→ water, from âb o havâ “weather; climate.”
Havâ, from Ar., probably itself a loanword from Mid.Pers. vây “weather, air,” Av. vayah-, vaya- “weather,” from va- “to blow;” cf. Skt. va-, Gk. aemi- “to blow;” Av. vâta- “wind,” Skt. vata-,
L. ventus, Mod. Pers. bâd “wind.” PIE *we- “to blow;” havâb contraction of havâ + âb “→ water,” from âb o havâ “weather,” literally “water and air.”

Geology: The various processes, such as the actions of wind, rain, temperature changes and so forth, which mechanically and chemically cause exposed rocks to decompose.

Etymology (EN): From → weather + → -ing.

Etymology (PE): Sâyand, from sâyidan “to touch, to rub,” variants sâbidan, pasâvidan;
Khotanese sauy- “to rub;” Sogdian ps’w- “to touch;” ultimately
Proto-Iranian *sau- “to rub.”

Geology: The various processes, such as the actions of wind, rain, temperature changes and so forth, which mechanically and chemically cause exposed rocks to decompose.

Etymology (EN): From → weather + → -ing.

Etymology (PE): Sâyand, from sâyidan “to touch, to rub,” variants sâbidan, pasâvidan;
Khotanese sauy- “to rub;” Sogdian ps’w- “to touch;” ultimately
Proto-Iranian *sau- “to rub.”

1. A network of fine threads constructed by a spider from fluid secreted by its spinnerets, used to catch its prey.
   

2. A complex system of interconnected elements (OxfordDictionaries.com)

Etymology (EN): M.E., from O.E. webb “woven fabric, woven work, tapestry,” from (cf. O.Sax. webbi, O.Norse vefr, Du. webbe, O.H.G. weppi, Ger. Gewebe “web”); Skt. ubhnati “he laces together,” Per. baftan “to weave,” as below; Gk. hyphe, hyphos “web;” PIE *webh- “to weave.”

Etymology (PE): Vap, variant of Mid.Pers. waf-, wap- “to weave;”
Baluchi gwapit, gwapt/gwap-, Yazdi vôpt/vôp- “to weave;” Mod.Pers. bâf-/bâftan; Av. ubdaēna- “made from woven material;” Proto-Ir. *uab/f “to weave;” cognate with web, as above.

1. A network of fine threads constructed by a spider from fluid secreted by its spinnerets, used to catch its prey.
   

2. A complex system of interconnected elements (OxfordDictionaries.com)

Etymology (EN): M.E., from O.E. webb “woven fabric, woven work, tapestry,” from (cf. O.Sax. webbi, O.Norse vefr, Du. webbe, O.H.G. weppi, Ger. Gewebe “web”); Skt. ubhnati “he laces together,” Per. baftan “to weave,” as below; Gk. hyphe, hyphos “web;” PIE *webh- “to weave.”

Etymology (PE): Vap, variant of Mid.Pers. waf-, wap- “to weave;”
Baluchi gwapit, gwapt/gwap-, Yazdi vôpt/vôp- “to weave;” Mod.Pers. bâf-/bâftan; Av. ubdaēna- “made from woven material;” Proto-Ir. *uab/f “to weave;” cognate with web, as above.

The → SI unit of → magnetic flux. It is equal to 10⁸ → maxwells.

See also: Named after German physicist Wilhelm Eduard Weber (1804-1891).

The → SI unit of → magnetic flux. It is equal to 10⁸ → maxwells.

See also: Named after German physicist Wilhelm Eduard Weber (1804-1891).

A physiological relationship stating that to make a sensation increase in arithmetical proportion, the stimulus must increase in geometrical progression. In acoustics, the → bel (B) unit is used to relate the intensity of sound to an intensity level corresponding to the human hearing sensation. Similarly, the division of stars into a scale of → magnitudes is based upon the Weber-Fechner law. Same as Fechner’s law.

See also: After Ernst Heinrich Weber (1795-1878), a German physician, was one of the first people to approach the study of the human response to a physical stimulus in a quantitative fashion, and Gustav Theodor Fechner (1801-1887), a German physicist who founded psycho-physics and proposed the mathematical formulation in 1860; → law.

A physiological relationship stating that to make a sensation increase in arithmetical proportion, the stimulus must increase in geometrical progression. In acoustics, the → bel (B) unit is used to relate the intensity of sound to an intensity level corresponding to the human hearing sensation. Similarly, the division of stars into a scale of → magnitudes is based upon the Weber-Fechner law. Same as Fechner’s law.

See also: After Ernst Heinrich Weber (1795-1878), a German physician, was one of the first people to approach the study of the human response to a physical stimulus in a quantitative fashion, and Gustav Theodor Fechner (1801-1887), a German physicist who founded psycho-physics and proposed the mathematical formulation in 1860; → law.

A glass prism of very small angle used as an optical element to divert the path of a beam of light for a particular purpose. → absorbing wedge.

Etymology (EN): M.E. wegge; O.E. wecg “a wedge,” cf. M.Du. wegge, Du. wig, O.H.G. weggi “wedge,” Ger. Weck “wedge-shaped bread roll.”

Etymology (PE): Gové “wedge;” Av. vada- “wedge,” ^xvaδa- “deadly weapon;” cf. Skt. vadhá- “killer, deadly weapon,” vadh- “to slay, kill;” Gk. othein “to push” (root of → osmosis).

A glass prism of very small angle used as an optical element to divert the path of a beam of light for a particular purpose. → absorbing wedge.

Etymology (EN): M.E. wegge; O.E. wecg “a wedge,” cf. M.Du. wegge, Du. wig, O.H.G. weggi “wedge,” Ger. Weck “wedge-shaped bread roll.”

Etymology (PE): Gové “wedge;” Av. vada- “wedge,” ^xvaδa- “deadly weapon;” cf. Skt. vadhá- “killer, deadly weapon,” vadh- “to slay, kill;” Gk. othein “to push” (root of → osmosis).

A photometer in which an → absorbing wedge is inserted in the brighter of two beams until the flux densities of the two light sources are equal.

See also: → wedge; → photometer.

A photometer in which an → absorbing wedge is inserted in the brighter of two beams until the flux densities of the two light sources are equal.

See also: → wedge; → photometer.

A division of time containing 7 successive days, which is completely independent of the month or the year. Unlike the month and the year, the week is an artificial unit of time, lacking an equivalent astronomical period.

Etymology (EN): M.E. weke; O.E. wice, cf. O.N. vika, M.Du. weke, O.H.G. wecha, Ger. Woche, akin to L. vicis “turn, change.”

Etymology (PE): Hafté “week, hebdomad,” from haft “seven” → hepta-.

A division of time containing 7 successive days, which is completely independent of the month or the year. Unlike the month and the year, the week is an artificial unit of time, lacking an equivalent astronomical period.

Etymology (EN): M.E. weke; O.E. wice, cf. O.N. vika, M.Du. weke, O.H.G. wecha, Ger. Woche, akin to L. vicis “turn, change.”

Etymology (PE): Hafté “week, hebdomad,” from haft “seven” → hepta-.

If a function φ(x) is continuous on a closed interval [a,b], then for every ε > 0 there exists a polynomial P(x) such that |f(x) - P(x)| <ε, for every x in the interval.

See also: After German mathematician Karl Wilhelm Theodor Weierstrass (1815-1897); → approximation; → theorem.

If a function φ(x) is continuous on a closed interval [a,b], then for every ε > 0 there exists a polynomial P(x) such that |f(x) - P(x)| <ε, for every x in the interval.

See also: After German mathematician Karl Wilhelm Theodor Weierstrass (1815-1897); → approximation; → theorem.

A test for uniform convergence of a sequence of functions. If there exists a series of numbers Σ M_i (summed from n = 1 to ∞), in which M_i≥ Σ |u_i(x)| for all x in the interval [a, b] and Σ M_i is convergent, the series u_i(x) will be uniformly convergent in that interval.

See also: → Weierstrass approximation theorem; M referring to → majorant; → test.

A test for uniform convergence of a sequence of functions. If there exists a series of numbers Σ M_i (summed from n = 1 to ∞), in which M_i≥ Σ |u_i(x)| for all x in the interval [a, b] and Σ M_i is convergent, the series u_i(x) will be uniformly convergent in that interval.

See also: → Weierstrass approximation theorem; M referring to → majorant; → test.

1. The force of attraction of the Earth on a given mass. → molecular weight; → weightlessness.
   

2. Statistics: A measure of the relative importance of an item in a statistical population. → weighted mean.
   

See also:

→ atomic weight, → counterweight, → mean molecular weight, → molecular weight, → statistical weight, → weight concentration, → weight fraction, → weight of a tensor density, → weight-fraction concentration, → weightlessness.

Etymology (EN): M.E., from O.E. gewiht, cf. O.N. vætt, O.Fris. wicht, M.Du. gewicht, Ger. Gewicht.

Etymology (PE): Vazn, loan from Ar. wazn.

1. The force of attraction of the Earth on a given mass. → molecular weight; → weightlessness.
   

2. Statistics: A measure of the relative importance of an item in a statistical population. → weighted mean.
   

See also:

→ atomic weight, → counterweight, → mean molecular weight, → molecular weight, → statistical weight, → weight concentration, → weight fraction, → weight of a tensor density, → weight-fraction concentration, → weightlessness.

Etymology (EN): M.E., from O.E. gewiht, cf. O.N. vætt, O.Fris. wicht, M.Du. gewicht, Ger. Gewicht.

Etymology (PE): Vazn, loan from Ar. wazn.

of a gas included in the composition of a → gas mixture, the ratio of mass of this gas to the mass of the whole mixture. Same as → weight fraction and → weight-fraction concentration.

See also: → weight; → concentration.

of a gas included in the composition of a → gas mixture, the ratio of mass of this gas to the mass of the whole mixture. Same as → weight fraction and → weight-fraction concentration.

See also: → weight; → concentration.

Same as → weight concentration.

See also: → weight; → fraction.

Same as → weight concentration.

See also: → weight; → fraction.

A constant the value of which is characteristic for any given → tensor density.

See also: → weight; → tensor; → density.

A constant the value of which is characteristic for any given → tensor density.

See also: → weight; → tensor; → density.

Same as → weight concentration.

See also: → weight; → fraction; → concentration.

Same as → weight concentration.

See also: → weight; → fraction; → concentration.

An mean which is obtained by combining different numbers according to the relative importance of each.

See also: → weight; → mean.

An mean which is obtained by combining different numbers according to the relative importance of each.

See also: → weight; → mean.

The phenomenon experienced by a body when there is no force of reaction on it. This happens when the body is in → free fall in a → gravitational field or when the net force on it is zero.

Etymology (EN): From → weight + -less suffix meaning “without”

• -ness a suffix of quality or state.

Etymology (PE): Bivazni, from bi- “without,” → a-,

• vazn, → weight, + -i.

The phenomenon experienced by a body when there is no force of reaction on it. This happens when the body is in → free fall in a → gravitational field or when the net force on it is zero.

Etymology (EN): From → weight + -less suffix meaning “without”

• -ness a suffix of quality or state.

Etymology (PE): Bivazni, from bi- “without,” → a-,

• vazn, → weight, + -i.

A → semiempirical → equation which describes the → binding energy of the → atomic nucleus. It is essentially a nuclear mass formula that provides the total binding energy per → nucleon as the sum of five terms:
E_b = a_VA - a_SA^2/3 - a_CZ²/A^1/3 - a_A(N -Z)²/A + δ(A,Z),
where the terms in the right-hand side of this equation are called the volume term, surface term, Coulomb term, asymmetry term, and pairing term, respectively. A, Z, and N are the number of nucleons, → protons, and → neutrons, respectively
(see, e.g., Alexi M. Frolov, 2013, arxiv.org/pdf/1212.6768). Also called Bethe-Weizacker formula and → semiempirical binding energy formula.

See also: Named after Carl Friedrich von Weizäcker (1912-2007), German physicist, who derived the formula in 1935, Z. für Physik 96, 431; → formula.

A → semiempirical → equation which describes the → binding energy of the → atomic nucleus. It is essentially a nuclear mass formula that provides the total binding energy per → nucleon as the sum of five terms:
E_b = a_VA - a_SA^2/3 - a_CZ²/A^1/3 - a_A(N -Z)²/A + δ(A,Z),
where the terms in the right-hand side of this equation are called the volume term, surface term, Coulomb term, asymmetry term, and pairing term, respectively. A, Z, and N are the number of nucleons, → protons, and → neutrons, respectively
(see, e.g., Alexi M. Frolov, 2013, arxiv.org/pdf/1212.6768). Also called Bethe-Weizacker formula and → semiempirical binding energy formula.

See also: Named after Carl Friedrich von Weizäcker (1912-2007), German physicist, who derived the formula in 1935, Z. für Physik 96, 431; → formula.

1. In a good or satisfactory manner; thoroughly, carefully, or soundly.
   

2. A hole drilled or bored into the earth to obtain water, petroleum, natural gas, brine, or sulfur (Dictionary.com).

Etymology (EN): 1) M.E., from O.E. wel(l) (cognates Du. wel, Ger. wohl).

2. M.E. well(e), O.E. wylle, wella, welle (cognates: O.Saxon wallan, O.Fris. walla, O.H.G. wallan, Ger. wallen “to bubble, boil”).

Etymology (PE): 1) Xoš “good, well, sweet, fair, lovely,” probably related to hu- “good, well,” → eu-. Xub, ultimately from Av. huuāpah- “doing good work,” → operate.

2. Câh “a well,” from Mid.Pers. câh “a well;”
   Av. cāt- “a well,” from kan- “to dig,” uskən- “to dig out;”
   O.Pers. kan- “to dig,” akaniya- “it was dug;” Mod.Pers.
   kandan “to dig;” cf. Skt. khan- “to dig,” khanati “he digs,” kha- “cavity, hollow, cave, aperture.”

1. In a good or satisfactory manner; thoroughly, carefully, or soundly.
   

2. A hole drilled or bored into the earth to obtain water, petroleum, natural gas, brine, or sulfur (Dictionary.com).

Etymology (EN): 1) M.E., from O.E. wel(l) (cognates Du. wel, Ger. wohl).

2. M.E. well(e), O.E. wylle, wella, welle (cognates: O.Saxon wallan, O.Fris. walla, O.H.G. wallan, Ger. wallen “to bubble, boil”).

Etymology (PE): 1) Xoš “good, well, sweet, fair, lovely,” probably related to hu- “good, well,” → eu-. Xub, ultimately from Av. huuāpah- “doing good work,” → operate.

2. Câh “a well,” from Mid.Pers. câh “a well;”
   Av. cāt- “a well,” from kan- “to dig,” uskən- “to dig out;”
   O.Pers. kan- “to dig,” akaniya- “it was dug;” Mod.Pers.
   kandan “to dig;” cf. Skt. khan- “to dig,” khanati “he digs,” kha- “cavity, hollow, cave, aperture.”

A string of → symbols from the alphabet of the → formal language that conforms to the grammar of the formal language. → closed wff, → open wff.

See also: Wff, pronounced whiff; → well; → form; → formula.

A string of → symbols from the alphabet of the → formal language that conforms to the grammar of the formal language. → closed wff, → open wff.

See also: Wff, pronounced whiff; → well; → form; → formula.

A set in which every → nonempty → subset has a minimum element.

See also: → well; → order; → set.

A set in which every → nonempty → subset has a minimum element.

See also: → well; → order; → set.

A sequence of → permitted transitions in the → ultraviolet from an → excited state (C) of the → molecular hydrogen (H₂) to the electronic → ground state, with ΔE > 12.3 eV and λ ranging from 1160 Å to 1250 Å. When a hydrogen molecule absorbs such a photon, it undergoes a transition from the ground electronic state to the excited state (C). The following rapid → decay creates an → absorption band in that wavelength range.
See also → Lyman band; → Lyman-Werner photon.

See also: Named after the Danish physicist Sven Theodor Werner (1898-1984), who discovered the band (S. Werner, 1926, Proc. R. Soc. London Ser. A, 113, 107); → band.

A sequence of → permitted transitions in the → ultraviolet from an → excited state (C) of the → molecular hydrogen (H₂) to the electronic → ground state, with ΔE > 12.3 eV and λ ranging from 1160 Å to 1250 Å. When a hydrogen molecule absorbs such a photon, it undergoes a transition from the ground electronic state to the excited state (C). The following rapid → decay creates an → absorption band in that wavelength range.
See also → Lyman band; → Lyman-Werner photon.

See also: Named after the Danish physicist Sven Theodor Werner (1898-1984), who discovered the band (S. Werner, 1926, Proc. R. Soc. London Ser. A, 113, 107); → band.

The direction 90° to the left or 270° to the right of → north.

Etymology (EN): M.E., O.E. “west” “in or toward the west;” cf. O.N. vestr, O.Fris., M.Du., Du. west, Ger. West; PIE base *wes- (Gk. hesperos, L. vesper “evening, west”).

Etymology (PE): Bâxtar “west;” Mid.Pers. apâxtar “north;” Av. apāxtar “northern.”

The direction 90° to the left or 270° to the right of → north.

Etymology (EN): M.E., O.E. “west” “in or toward the west;” cf. O.N. vestr, O.Fris., M.Du., Du. west, Ger. West; PIE base *wes- (Gk. hesperos, L. vesper “evening, west”).

Etymology (PE): Bâxtar “west;” Mid.Pers. apâxtar “north;” Av. apāxtar “northern.”

Lying toward or situated in the west. → greatest western elongation.

See also: Adjective from → west.

Lying toward or situated in the west. → greatest western elongation.

See also: Adjective from → west.

The position of a planet when it is visible in the eastern sky before dawn.

See also: → western; → elongation.

The position of a planet when it is visible in the eastern sky before dawn.

See also: → western; → elongation.

Consisting of, containing, covered or soaked with water or some other liquid.

Etymology (EN): O.E. wæt “moist, liquid,” related to O.Frisian wēt, O.N. vātr, O.E. wæter “water.”

Etymology (PE): Xis, xês “wet, moist,” related to pašang, pašangidan “sprinkle,” ultimately from Proto-Ir. *haic- “to pour (out), moisten;” cf. Av. haēc- “to pour (out); to irrigate;” Khotanese häs- “to wet, besprinkle;” Sogd. šync “to pour” (Cheung 2007).

Consisting of, containing, covered or soaked with water or some other liquid.

Etymology (EN): O.E. wæt “moist, liquid,” related to O.Frisian wēt, O.N. vātr, O.E. wæter “water.”

Etymology (PE): Xis, xês “wet, moist,” related to pašang, pašangidan “sprinkle,” ultimately from Proto-Ir. *haic- “to pour (out), moisten;” cf. Av. haēc- “to pour (out); to irrigate;” Khotanese häs- “to wet, besprinkle;” Sogd. šync “to pour” (Cheung 2007).

A merger between → gas-rich galaxies. Wet mergers may lead to enhanced star formation, trigger → active galactic nuclei, and transform a → disk galaxy into an → elliptical galaxy. The larger the → redshift, the wetter mergers should be.

See also: → wet; → merger.

A merger between → gas-rich galaxies. Wet mergers may lead to enhanced star formation, trigger → active galactic nuclei, and transform a → disk galaxy into an → elliptical galaxy. The larger the → redshift, the wetter mergers should be.

See also: → wet; → merger.

The → world lines of galaxies form in the 4D space-time
a bundle of non-intersecting → geodesics orthogonal to a series of space-like hyperstructures (e.g. Narlikar 2002, An Introduction to Cosmology, 3rd Edition, Cambridge Univ. Press). Expressed differently: The world lines of galaxies, or “fundamental particles,” form (on average) a space-time filling family of non-intersecting geodesics converging toward the past (Rugh & Zinkernagel, 2010, astro-ph/1006.5848). The statement is sometimes denoted postulate, assumption, or hypothesis. The importance of Weyl’s principle is that it asserts that cosmic matter moves according to certain regularity requirements. See also → cosmological principle.

See also: First introduced by the German mathematician Hermann Weyl (1885-1955) in 1923 in his Raum, Zeit, Materie; → principle.

The → world lines of galaxies form in the 4D space-time
a bundle of non-intersecting → geodesics orthogonal to a series of space-like hyperstructures (e.g. Narlikar 2002, An Introduction to Cosmology, 3rd Edition, Cambridge Univ. Press). Expressed differently: The world lines of galaxies, or “fundamental particles,” form (on average) a space-time filling family of non-intersecting geodesics converging toward the past (Rugh & Zinkernagel, 2010, astro-ph/1006.5848). The statement is sometimes denoted postulate, assumption, or hypothesis. The importance of Weyl’s principle is that it asserts that cosmic matter moves according to certain regularity requirements. See also → cosmological principle.

See also: First introduced by the German mathematician Hermann Weyl (1885-1955) in 1923 in his Raum, Zeit, Materie; → principle.

The star δ Canis Majoris, magnitude 1.84. It is an F8 supergiant 1800 light-years away. Among bright stars, Wezen is one of the most distant and luminous. Its luminosity is 50,000 times that of the Sun. Other designations: Alwazn, Wesen, HR 2693, HD 54605.

Etymology (EN): From Ar. Al-wazn (الوزن) “weight.”

Etymology (PE): Vazn, from Ar. Al-wazn, as above.

The star δ Canis Majoris, magnitude 1.84. It is an F8 supergiant 1800 light-years away. Among bright stars, Wezen is one of the most distant and luminous. Its luminosity is 50,000 times that of the Sun. Other designations: Alwazn, Wesen, HR 2693, HD 54605.

Etymology (EN): From Ar. Al-wazn (الوزن) “weight.”

Etymology (PE): Vazn, from Ar. Al-wazn, as above.