An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

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.

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.

From Gk. lepto-, combining form of leptos "thin, slight" + → kurtosis.

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.

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).

→ 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.

→ 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.

→ lepton; → number.

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

L. lepus "hare."

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.

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.

M.E., from O.Fr. letre "character, letter; missive," from L. littera "letter of the alphabet," litterae (plural) "epistle, literature"

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.

From O.Fr. livel, from L. libella "a balance, level," diminutive of libra "balance, scale."

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.

→ 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.

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.

Ahrom, of unknown etymology.

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

→ 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.

From L. levitas "lightness," from levis "light."

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.

→ 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-.

From L. laevo-, from laevus, cf. Gk. laios, Russ. levyj, + epenthetic vowel -o-.

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.

Adj. related to → levorotation.

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

Adj. related to → levorotation.

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

→ 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.

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.

Vâžešnâsi, from vâžé, → word, + -šenâsi, → -logy.