An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 12929 Search : far
Rayleigh's criterion
  سنجیدار ِ ریلی   
sanjidâr-e Rayleigh

Fr.: critère de Rayleigh   

A criterion for the instability of a basic swirling flow with an arbitrary dependence of angular velocity Ω(r) on the distance r from the axis of rotation. This states that in → inviscid fluids: Ω(r) < 0 for instability, where Ω = (1/r3) (d/dr)(r4Ω4).

Rayleigh; → criterion.

Rayleigh-Jeans law
  قانون ِ ریلی-جینز   
qânun-e Rayleigh-Jeans(#)

Fr.: loi de Rayleigh-Jeans   

A classical law approximately describing the intensity of radiation emitted by a → blackbody. It states that this intensity is proportional to the temperature divided by the fourth power of the wavelength (8πkT4). The Rayleigh-Jeans law is a good approximation to the experimentally verified Planck radiation formula only at long wavelengths. At short wavelengths it runs into a paradox named the → ultraviolet catastrophe.

Rayleigh; → Jeans; → law.

Rayleigh-Jeans spectrum
  بیناب ِ ریلی-جینز   
binâb-e Rayleigh-Jeans

Fr.: spectre Rayleigh-Jeans   

The part of → electromagnetic spectrum approximated by the → Rayleigh-Jeans law.

Rayleigh; → Jeans; → spectrum.

Rayleigh-Taylor instability
  ناپایداری ِ ریلی-تیلر   
nâpâydâri-ye Rayleigh-Taylor

Fr.: instabilité Rayleigh-Taylor   

A type of hydrodynamical instability between two fluids of different densities, which occurs when the heavy fluid lies above the lighter fluid in a gravitational field. More generally a material interface is said to be Rayleigh-Taylor unstable whenever the fluid acceleration has an opposite direction to the density gradient.

rayleigh; → Taylor number; → instability.

Réaumur scale
  مرپل ِ ریءومور   
marpel-e Réaumur

Fr.: échelle Réaumur   

A temperature scale in which the → freezing point and the → boiling point of → water are set to 0 and 80 degrees respectively. See also → Celsius scale, → Fahrenheit scale, → Kelvin scale, → Rankine scale.

Named after René Antoine Ferchault de Réaumur (1683-1757), who first proposed it in 1730; → scale.

RCW catalogue
  کاتالوگ ِ WCR   
kâtâlog-e RCW

Fr.: catalogue RCW   

A catalog of → H II regions in the → southern  → Milky Way based on observations obtained at Mount Stromlo Observatory (Australia). It contains 181 → H-alpha emission objects characterized by their positions, dimensions, and estimated brightness.

Rodgers,A.W., Campbell, C.T., Whiteoak, J.B., 1960, MNRAS, 121, 103; → catalog.

re-
  وا-، باز-   
vâ- (#), bâz- (#)

Fr.: re-   

A prefix meaning "again, anew" to indicate repetition (as rebuild, retell), "back, backward" to indicate "withdrawal" or "backward motion" (react, recall), or sometimes merely intensive (refine, resolve).

M.E., from O.Fr., from and L. re- "again, back."

Vâ-, variant bâz-, prefix denoting "reversal, opposition; separation; repetition; open; off; away," from Mid.Pers. abâz-, apâc-; O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from," apaš [adv.] "toward the back;" cf. Skt. ápāñc "situated behind."

react
  واژیریدن   
vâžiridan

Fr.: réagir   

1) To act in response to an agent, influence, or stimulus.
2) To act in a reverse direction or manner; to act in opposition, as against some force.
3) Chem.: To undergo a → chemical reaction.

re-; → act.

reactance
  واژیرایی   
vâžirâyi

Fr.: réactance   

The opposition to the flow of alternating current caused by the inductance and capacitance in a circuit rather than by resistance.

From → react + -ance a suffix of nouns.

Vâžirâyi state noun of vâžirâ agent noun of vâžiridanreact.

reactant
  واژیرا   
vâžirâ

Fr.:   

1) General: A person or thing that reacts.
2) A substance on the left side of a → chemical equation.

From → react + -ant.

reaction
  واژیرش، واکنش   
vâžireš, vâkoneš

Fr.: réaction   

1) General: Action in response to some influence, event, stimulus.
2) An equal and opposite force exerted by a body against a force acting upon it. → principle of action and reaction.
3) A → nuclear reaction; → chain reaction.
4) → chemical reaction.

Verbal noun of → react.

reaction rate
  نرخ ِ واژیرش   
nerx-e vâžireš

Fr.: taux de réaction   

The speed with which a → chemical reaction takes place. In other words, the change in → concentration of a → substance divided by the → time interval during which the change is observed.

reaction; → rate.

reactive
  واژیرنده؛ واژیرشی   
vâžirandé; vâžireši

Fr.: réactif   

Tending to react. Pertaining to or characterized by reaction.

From → react + -ive a suffix of adjectives expressing tendency, disposition, function, connection, etc.

Vâžirandé verbal adj. of vâžiridanreact; vâžireši, adj. of vâžirešreaction.

reactivity
  واژیرندگی   
vâžirandegi

Fr.: réactivité   

1) General: The quality or condition of being reactive.
2) Physics: A measure of the deviation from the condition at which a → nuclear reactor is critical.
3) Chem.: The relative → capacity of an → atom, → molecule, or → redical to undergo a → chemical reaction with another atom, molecule, or → compound.

From → reactive + → -ity.

reactor
  واژیرگر   
vâžirgar

Fr.: réacteur   

1) A device for introducing reactance into an electrical circuit (e.g. a capacitor).
2) Same as → nuclear reactor.

From → react + → -or.

reactor core
  مغزه‌ی ِ واژیرگر   
maqze-ye vâžirgar

Fr.: cœur de réacteur   

The part of a → nuclear reactor in which → nuclear fission takes place and huge quantities of heat energy are generated.

reactor; → core.

reading rate
  نرخ ِ خوانش   
nerx-e xâneš

Fr.: vitesse de lecture   

In computing and data processing, the number of words, characters, fields, etc. sensed by an input sensing device per unit of time.

Reading, verbal noun of read, from M.E. reden, O.E. rædan, redan "to counsel, read;" cf. Du. raden, Ger. raten "to advise, counsel, guess;" akin to Skt. rādh- "to succeed, accomplish;" Gk. arithmos "number amount;" L. ratio; Pers. rây, râ "because of, for the sake of;" → reason; → rate.

Nerx, → rate; xâneš verbal noun of xândan "to read; to sing; to call;" Mid.Pers. xwân- "to resound; to call;" Av. xvan- "to sound," Proto-Iranian *huan- "to call;" cf. Skt. svan-, sváranti "to sound, make a sound, sing;" L. sonus "sound," sonare "to sound;" O.E. swinn "music, song," PIE base *suen- "to sound" (Cheung 2007).

readout noise
  نوفه‌ی ِ خوانش   
nufe-ye xâneš

Fr.: bruit de lecture   

The noise added in the process of reading a detector such as a CCD.

reading rate; → noise.

reagent
  واکنشگر   
vâkonešgar

Fr.: réactif   

A chemical substance that, because of the reactions it causes, is used to detect, measure, or prepare another substance.

From re(act) + → agent.

Vâkonešgar, from vâ-, → re-, + konešgaragent.

real
  هسیا   
hasyâ

Fr.: réel   

1) General: Having actual physical existence; genuine, not artificial.
2) Math.: Involving, relating to, or having elements of the set of rational or irrational numbers only.
3) Philo.: Existent or pertaining to the existent as opposed to the nonexistent; actual as opposed to possible or potential.
See also:
real dynamical variable, → real equator, → real equinox, → real fluid, → real gas, → real image, → real number, → real object, → real-time operation, → real-time processing, → realism, → realist, → realistic, → reality, → true.

M.E., from O.Fr. reel, from L.L. realis "relating to things; actual," from L. res "matter, thing," of unknown origin.

Hasyâ, from O.Pers. hašya- "true, real;" Av. haiθa- "true, real;" cf. Khotanese hiththo "true, real;" Ossetic aecaeg "true, real, genuine;" Skt. satyá- "true, real, genuine;" PIE base *es- "to be" (Mod.Pers. hastan, astan "to be;" O.Pers./Av. ah-, Skt. as-).

<< < -es -iv -ti 217 a- abe abs abs acc acc ach act act ada adi adv aff agg Alc Alf ali all alp alt Ama amp ana ang ang ann ano ant ant ape apo app aps arc arg arm art ass ast ast ast atm ato att aur aut axi B-t bai Bal bar bar Be bee Bes bi- bif bin bin bio bis bla bli blu Boe Bol bor bou bra bri Bro bum CAI cal Can cap car car cat cat CCD Cel cen CGS cha cha che che chr cir cir civ cla clo clo CMB coa coe coh col col col Com com com com com com com com com con con con con con con con con con con con coo cor cor cor cos cos cos cou cov cra cri cro cry cum cur cyc d'A dar dat DC dea dec dec dec def def deh Del den dep des det dev dia dif dif dif dim dip dir dis dis dis dis dis div dom dou dou dri dup dus dyn dyn ear eas ecl Edd eff Ein Ekm ele ele ele ele ell emb emi enc ene ent eph equ equ equ eru eth eup eve EX exc exe exi exo exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla flo flu fog for for Fou fra fre Fre Fro fus G-t gal gal Gam gas Gau Gem gen geo geo geo gia gla gol gra gra gra gra Gre Gre gui H a haf Hal har har He- hea hel Hel her Her hie hig his hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima imp imp imp inc ind ind ine inf inf Inf inj InS ins int int int int int int int int inv inv ion iro Isl iso iso Jac jet jud jur Kel Kep kil kly L d Lag lam Lap lar lat law Lea len lep lib lig lin lin lin liq lit loc log lon Los low lum lun Lut Lyr mac mag mag mag mag mag maj man Mar mas mas mat mea mec mem mer mes met met met mic mid mil min Mir Miz mod mol mon moo MOS mul mul mut nai nas nat neb neg Neu neu New New Nih noi non non non nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove oxi pac Pal par par Par par pas Pau Pel per per per per per per pha phi pho pho pho phy pip Pla pla pla pla pla Plu Poi pol pol pol pop pos pos pot Pra pre pre pre Pri pri pri pro pro pro pro pro pro pro Pto pul puz qua qua qua qua qui rad rad rad rad rad rad rai ran Ras Ray rea rec rec rec red red ref reg reg rel rel rel rep res res res res rev rhe Rie Rig Rit roe Ros rot Ruf Ryd Sag sam sat sca sca Sch Sco sec sec sec seg sel sem sen set sha SHB sho sib sie sil sim sin sit sky slo sno sod sol sol sol sol sor sou Spa spa spe spe spe sph spi Spi spr sta sta sta sta sta ste ste Ste sto str str sub sub sub suf sun sup sup sup sup sur swo syn sys tak Tay Tel ten ter tet the the the thi Tho thu tid tim toa top tot tra tra tra tra tri tri tro Tru tur twi Typ UBV ult unb uni uni uni up ura uti val var vec Vel ver ver vig vir vis VLT vol wad was wav wav wea wei Whe Wie win WN5 Wol X-r yea You zer zod > >>