An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 701
rare earth element
  بن‌پار ِ خاکی ِ کمیاب، خاک ِ کمیاب   
bonpâr-e xâki-ye kamyâb, xâk-e kamyâb

Fr.: terre rare   

Any of the group of metallic → chemical elements with → atomic numbers between 57 and 71 inclusive. The name is an inappropriate terminology, since they are neither rare nor earth; preferred name → lanthanide.

rare; → earth; → element.

rare gas
  گاز ِ کمیاب   
gâz-e kamyâb (#)

Fr.: gaz rare   

Another name for → inert gas.

M.E., from O.Fr. rere "sparse," from L. rarus "loose, wide apart, thin, infrequent;" &rar; gas.

Kamyâb "rare, difficult to find," from kam "little, few; deficient, wanting; scarce" (Mid.Pers. kam "little, small, few," O.Pers./Av. kamna- "small, few"); + yâb present stem of yâftanyâftan, yâbidan "to find, discover; to obtain, acquire" (Mid.Pers. ayâftan, ayâpênitan "to reach, attain;" Manichean Mid.Pers. 'y'b "to attain;" Parthian, Sogdian (+ *pati-) pty'b "to reach, obtain;" Av. ap- "to reach, overtake," apayeiti "achieved, reached;" Skt. âp- "to reach, gain," âpnoti "reaches, gains;" Gk. hapto, haptomai "to touch, cling to, adhere to;" L. apiscor "touch, reach;" PIE base *ap- "to take, reach").


Fr.: raréfaction   

The state of being rarefied, less dense.
An instantaneous reduction in density of a gas resulting from passage a sound wave; opposite of → compression.

M.E. rarefien, from M.Fr. rarefier, from L. rarefacere "make rare," from rarus "loose, wide apart, thin, infrequent."

Verbal noun from âlar present stem of âlaridanrarefy + , a suffix.

rarefaction wave
  موج ِ آلرش   
mowj-e âlareš

Fr.: onde de raréfaction   

A pressure wave in a fluid generated by rarefaction. It travels in the opposite direction to that of a shock wave in the medium.

rarefaction; → wave.

rarefied gas
  گاز ِ آلریده   
gâz-e âlaridé

Fr.: gaz raréfié   

A gas whose pressure is much less than a reference pressure.

Past participle of → rarefy; → gas.


Fr.: raréfier   

1) To make less dense.
2) To become less dense; become thinned.
Related concepts: → attenuate, → dilute, → decompress.

M.E. rarefien, from M.Fr. rarefier, from rare, combining form of rarus "loose, wide apart, thin, infrequent."

Alaridan, infinitive of âlar, from intensive/nuance prefix â- + lar "thin, meagre" (Dehxodâ), Lori, Laki larr, larrek "thin cow or sheep," Kurd. lerr "thin, lean," variants of laqar (Torbat-Heydariyé), lâqar "lean, meagre, slender; weak."

Rasalgethi (α Herculis)
Ra's-el-jâsi (#)

Fr.: Rasalgethi   

The brightest star in the constellation → Hercules. It is a → red supergiant of type M5 (surface temperature about 3300 K) lying at a distance of 380 light-years. Rasalgethi is a variable star with a mean magnitude of V = 3.48. It has a fifth magnitude companion 5'' away. This secondary is itself a double that consists of a 4 solar-mass class G5 giant star with a temperature about that of the Sun and a 2.5 solar-mass F2 dwarf star (somewhat hotter than the Sun) in orbit around each other separated by 0.4 AU with a 52 day period.

Rasalgethi, from Ar. Ra's al-Jathi (رأس‌الجاثی) "the Kneeler's Head," in reference to an early name for the constellation, the figure of the man seen upside down, his head toward the south, from ra's "head" + jathi "kneeling."

Rasalhague (α Ophiuchi)
ra's-el-hayyé (#)

Fr.: Rasalhague   

The brightest star (V = 2.08) in the constellation → Ophiuchus. Rasalhague is a → giant star of type A5 lying 47 light-years from Earth. It has a faint, very close companion only 0''.5 away, 7 A.U., that orbits with a period of 8.7 years.

Rasalhague, from Ar. Ra's al-Hayyah (رأس‌الحیه), literally the "head of the snake," from ra's "head" + Hayyah "snake," referring to the creature in Gk. mythology.


Fr.: taux   

The amount of change of some quantity during a time interval divided by the length of the time interval.

M.E. rate "monetary value," M.Fr. rate "price, value," from M.L. rata (pars) "fixed (amount)," from L. rata "fixed, settled," p.p. of reri "to reckon, think," → reason.

Nerx "rate, price, tariff."


Fr.: rapport   

Math.: The quotient of two quantities arrived at by dividing one by the other.

From L. ratio "reckoning, calculation," also "reason," from rat-, p.p. stem of reri "to reckon, calculate," also "think," → reason.
Fr. rapport, back-formation from rapporter "bring back," from → re- "back, again" + apporter "to bring," from L. apportare "to bring," from → ad- "to" + portare "to carry."

Vâbar, on the model of Fr. rapport "bringing back," as above, from vâ- prefix meaning "back to the original place, again," → re-, + bar present stem of bordan "to carry, lead" (Mid.Pers. burdan, O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive)," Skt. bharati "he carries," Gk. pherein, L. fero "to carry;" PIE base *bher- "to carry").

  ۱) راینی، راینوار؛ ۲) خردانه، خردمندانه؛ ۳) وابری   
1) râyani, râyanvâr; 2) xeradâné, xeradmandâné; 3) vâbari

Fr.: rationnel   

1) Having or exercising the ability to → reason.
2) Consistent with or based on reason; logical; in accordance with sound reasoning.
3) Math.: Capable of being expressed as a quotient of integers.

M.E. racional, from O.Fr. racionel, from L. rationalis "of or belonging to reason, reasonable," from ratio (genitive rationis) "reckoning, calculation, reason," from rat-, pp. stem of reri "to reckon, calculate; consider, think."

1) Râyani, of or pertaining to râyan, → reason.
2) Xeradâné, xeradmandâné, of or pertaining to xerad "understanding, judgement, intellect, wisdom;" Mid.Pers. xrad "reason, intellect, intelligence, wisdom, understanding;" O.Pers. xraθu- "wisdom;" Av. xratu- "intelligence, undestanding, wisdom; will, purpose, council;" cf. Skt. krátu- "power, will-power;" Gk. kratos "power, strength."
3) vâbari, of or pertaining to vâbar, → ratio.

rational number
  عدد ِ وابری   
'adad-e vâbari

Fr.: nombre rationnel   

Any number that can be expressed as a ratio of two integers, providing the second number is not zero.

rational; → number.


Fr.: raisonnement, exposé raisonné   

1) The fundamental reason or reasons serving to account for something.
2) A statement of reasons.
3) A reasoned exposition of principles (

L. neuter of rationalis.

Râyanâl, from râyan, → reason, + -âl, → -al.

  راین‌باوری، خردباوری   
râyan-bâvari, xerad-bâvari

Fr.: rationalisme   

A philosophical doctrine that holds that → reason alone, unaided by experience, can arrive at basic truth regarding the world.

From → rational + -ism a Gk. suffix used in the formation of nouns denoting action or practice, state or condition, principles, doctrines, and so forth.

Râyan, → reason; xerad, → rational; bâvari, from bâvar "belief" (Mid.Pers. wâbar "beleif;" Proto-Iranian *uar- "to choose; to convince; to believe;" cf. Av. var- "to choose; to convince" varəna-, varana- "conviction, faith;" O.Pers. v(a)r- "to choose; to convince;" Skt. vr- "to choose," vara- "choosing").

varâq (#)

Fr.: corbeau   

Any of several large, corvine birds having lustrous, black plumage and a loud, harsh call, especially Corvus corax, of the New and Old Worlds (

M.E., from O.E. hræfn, hrefn; cf. O.N. hrafn, Dan. ravn, Du. raaf, O.H.G. hraban, Ger. Rabe "raven," O.E. hroc "rook," from PIE root *ker-, → crow.

Varâq, from Mid.Pers. varâγ "crow."

raw data
  داده‌های ِ خام   
dâdehâ-ye xâm

Fr.: données brutes   

Data that are unprocessed or not yet subjected to analysis.

Raw, from M.E., from O.E. hreaw "uncooked, raw;" cf. M.Du. rau, O.H.G. hrawer, Ger. roh; PIE base *krowos "congealed, bloody" cf. Skt. kravis- "raw flesh," krura- "bloody, raw, hard;" Gk. kreas "flesh;" L. crudus "not cooked," cruor "thick blood;" Lith. kraujas, O.C.S. kruvi "blood;" → data.

Dâdehâdata; xâm "crude, uncooked;" Mid.Pers. xâm "crude, raw" (Khotanese hāma- "raw;" Ossetic xom "raw;" Pash. ôm "raw"); cf. Skt āmá- "raw, uncooked;" Gk. omos "raw, uncooked."

partow (#)

Fr.: rayon   

1) Any of the lines or streams in which light appears to radiate from a luminous body. → light ray.
2) The straight line normal to the wave front in the propagation of radiant energy.
3) A stream of material particles all moving in the same straight line.

M.E. raie, raye, from O.Fr. rai "ray, spoke," from L. → radius "ray, spoke, staff, rod."

Partow, ultimately from Proto-Iranian *pari-tap- "to shine around, radiate away." The first component *pari- "around, about;" cf. Mod.Pers. par-, pirâ- "around, about," from Mid.Pers. pêrâ; O.Pers. pariy "around, about," Av. pairi "around, over," per- "to pass over, beyond;" Skt. pari; Gk. peri "around, about, beyond;" L. per "through;" PIE base *per- "through, across, beyond." The second component *tap- "to shine, radiate;" cf. Mod.Pers. tâbidan, variants tâftan "to shine," tafsidan "to become hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian t'b "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "; to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."

ray of class 1
  پرتو ِ رده‌ی ِ ۱   
partw-e rade-ye 1

Fr.: rayon de classe 1   

In → rainbows, a sun ray directly reflected from the surface of a water → droplet.

ray; → class.

ray of class 2
  پرتو ِ رده‌ی ِ ۲   
partw-e rade-ye 2

Fr.: rayon de classe 2   

In → rainbows, a sun ray transmitted directly through a water → droplet.

ray; → class.

ray of class 3
  پرتو ِ رده‌ی ِ ۳   
partw-e rade-ye 3

Fr.: rayon de classe 3   

In → rainbows, a sun ray that emerges from a water → droplet after one internal reflection. Rays of class 3 give rise to the → primary rainbow.

ray; → class.

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