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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<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu 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 con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>

Number of Results: 13048 Search : far
fine
  نازک   
nâzok (#)

Fr.: fine   

Very thin or slender. → fine structure, → fine-structure constant.

M.E. fin, from O.Fr. fin "perfected, of highest quality," from L. finis "end, limit."

Nâzok "thin, slender, subtle," from Mid.Pers. nâzuk "tender, gentle," variant nâzik, from nâz "joy, pride, glory" + → -ik.

fine dust
  ریزگرد، غبار ِ نازک   
rizgard, qobâr-e nâzok

Fr.: poussière fine   

Meteorology: An → inhomogeneous  → mixture of tiny, part → solid, part → liquid or → gaseous  → particles that are, in average, smaller than ten → microns. The constituents are soot, heavy metals, organic substances, and dioxins. The smaller these dust particles, the deeper they penetrate into the lung. Larger particles are intercepted by mucous membrane in nose, mouth, and throat but smaller particles can penetrate the smallest lung bronchioles and may cause severe damage (various respiratory disorders, lung cancer) → particulate matter.

fine; → dust.

fine structure
  ساختار ِ نازک   
sâxtâr-e nâzok

Fr.: structure fine   

Closely spaced components seen at high resolution in a → spectral line. The phenomenon is explained by the fact that instead of a single → energy level corresponding to a given value of the → quantum number  n, there are actually a number of energy levels lying close to one another. → fine-structure constant, → fine-structure line.

fine; → structure.

fine-structure constant
  پایای ِ ساختار ِ نازک   
pâyâ-ye sâxtâr-e nâzok

Fr.: constante de la structure fine   

A measure of the strength of → interaction between a → charged particle and the → electromagnetic field. It is a → dimensionless number expressed (in → cgs units) by α = e2c, where e is the → electron charge, ħ is the → reduced Planck's constant, and c is the → speed of light. It is approximately equal to 1/137 or 7.3 x 10-3. The smallness of this number is of great importance since it determines the size of → atoms and the → stability of → matter.

fine structure; → constant.

fine-structure line
  خط با ساختار ِ نازک   
xatt bâ sâxtâr-e nâzok

Fr.: raie de structure fine   

A → spectral line whose → energy levels have a → fine structure. Examples are [C II] 157.7 μm (→ singly ionized carbon), [O III] 88 μm, and [Ne II] 12.8 μm.

fine; → structure; → line.

finger
  انگشت   
angošt (#)

Fr.: doigt   

Any of the terminal members of the hand, especially one other than the thumb (Dictionary.com).

M.E., from O.E. fingor, cognate with Ger. Finger, Du. vinger, O.N. fingr, Goth. figgrs.

Angošt, variants angol, angul (also angal "loop"); Mid.Pers. angust; Av. angušta- "toe," ank- "curved, crooked;" cf. Skt. angustha- "thumb," angula- "finger," ankah "hook, bent;" Gk. angkon "elbow," angkura "anchor;" L. angulum "corner;" Lith. anka "loop;" O.E. ancleo "ankle;" O.H.G. ango "hook;" PIE *ang-/*ank- "to bend".

fingering convection
  همبز ِ انگشتوار   
hambaz-e angoštvâr

Fr.:   

A weak yet important kind of mixing that results from → fingering instability in stars within → radiative zones that have an unstable mean → molecular weight  → gradient. Also called → thermohaline convection.

finger; → -ing; → convection.

fingering instability
  ناپایداری ِ انگشتوار   
nâpâydâri-ye angoštvâr

Fr.: instabilité à traines   

A type of instability that often occurs in fluids which are thermally stably stratified, but have an inhomogeneous composition. A well-known example, found in upper layers of the Earth's oceans, is → salt fingers. Similar fingering instabilities can occur in any other thermally stably stratified solution, provided the concentration of the slower-diffusing solute increases with height. The saturated state of this instability, → fingering convection, takes the form of tightly-packed, vertically-elongated plumes of sinking dense fluid and rising light fluid, and significantly enhances the vertical transport of both heat and chemical composition. The fingering instability occurs in stars within radiation zones that have an unstable mean → molecular weight  → gradient (μ gradient). This situation is often found as a result of material accretion onto a star by anything from a single or multiple planets, to material from a dust-enriched or debris accretion disk, or material from a more evolved companion. It also naturally arises in the vicinity of the → hydrogen shell burning in → red giant branch (RGB) stars, and in thin element-rich layers near the surface of intermediate-mass stars. The fingering instability initially takes the form of thin tubes, hence the name "finger," within which the fluid moves vertically. The tubes rapidly break down, however, as a result of parasitic shear instabilities that develop inbetween them, and the fingering instability eventually saturates into a state of homogeneous fingering convection where the typical aspect ratio of the eddies is closer to one (P. Garaud et al., 2015, arXiv:1505.07759).

finger; → -ing; → instability.

fingers of God
  انگشتان ِ خدا   
angoštân-e Xodâ

Fr.: doigts de Dieu   

A → redshift space distortion which causes the dense central regions of → galaxy clusters to appear elongated along the → line of sight. This effect is attributed to random velocities in clusters of galaxies deviating from pure → Hubble flow. For an observer galaxies with peculiar velocity perpendicular to the line of sight do not change the redshift, which is given just by the normal Hubble expansion. On the contrary, galaxies with peculiar velocity along the line of sight appear with a different redshift, resulting from the Hubble expansion velocity plus the peculiar velocity. Since this affects only redshift and not position on the sky, the stretching occurs only radially, toward the observer. See also → Kaiser effect, → peculiar velocity.

finger; → God.

finite
  کرانمند   
karânmand (#)

Fr.: fini   

1) Math: The opposite of → infinite.
2) Physics: Either non-infinite or non-zero.

From L. finitus, p.p. of finire "to limit, set bounds, end."

Karânmand, from karân "boundary, side, end, coast" + -mand adjective suffix. Karân, variants karâné, kenâr, from Mid.Pers. karân, karânak, kenâr "edge, limit, boundary," Av. karana- "side, boundary, end."

finite population
  پرینش ِ کرانمند   
porineš-e karânmand

Fr.: population finie   

A → statistical population consisting of individuals or items which are finite in number.

finite; → population.

finite series
  سری ِ کرانمند   
seri-ye karânmand (#)

Fr.: série finie   

A sum a1 + a2 + a3 + · · · + aN, where the ai's are real numbers. In terms of Σ-notation, it is written as a1 + a2 + a3 + · · · + aN = Σ (n = 1 to N).  See also → infinite series.

finite; → series.

finite set
  هنگرد ِ کرانمند   
hangard-e karânmand

Fr.: ensemble fini   

A → set whose elements can be numbered from 1 to n, for some positive integer n.

finite; → set.

fire
  آتش، تش، آذر   
âtaš(#), taš (#), âzar (#)

Fr.: feu   

A state, process, or instance of combustion in which a substance combines with oxygen producing heat, light, and flame.

O..E. fyr, from P.Gmc. *fuir (cf. O.N. fürr, M.Du. vuur, Ger. Feuer), from PIE *paewr-; cf. Mod.Pers. Lori porpor "blazing charcoal," Gilaki bur, biur "smokeless red fire" (Lori perisk, periska "spark," Kurd. biriske "spark," Lârestâni pelita "spark"); Tokharian por, puwar "fire;" Gk. pyr "fire;" Hitt. pahhur "fire;" Skt. pū- "to cleanse."

Âtaš, variants âzar, taš, from Mid.Pers. âtaxš, âtur "fire;" Av. ātar-, āθr- "fire," singular nominative ātarš-; O.Pers. ātar- "fire;" Av. āθaurvan- "fire priest;" Skt. átharvan- "fire priest;" cf. L. ater "black" ("blackened by fire"); Arm. airem "burns;" Serb. vatra "fire;" PIE base *āter- "fire."

fireball
  تشگوی، آذرگوی   
tašguy (#), âzarguy (#)

Fr.: boule de feu   

A → meteor that is brighter than the brightest planets, i.e. with an apparent magnitude of -5 or greater. Fireballs are often followed by → meteorite falls. Also called → bolide.

From → fire + ball, from O.E., from O.N. bollr "ball," from P.Gmc. *balluz (cf. O.H.G. ballo, Ger. Ball), from PIE base *bhel- "to swell."

Tašguy, from taš "fire," variant of âtašfire + guy "ball, sphere," variants golulé, gullé, goruk, gulu, gudé (cf. Skt. guda- "ball, mouthful, lump, tumour," Pali gula- "ball," Gk. gloutos "rump," L. glomus "ball," globus "globe," Ger. Kugel, E. clot; PIE *gel- "to make into a ball").

first
  نخست، نخستین، یکم، آغاز   
naxost (#), naxostin (#), yekom (#), âqâz (#)

Fr.: premier   

Being before all others with respect to time, order, importance, etc., used as the ordinal number of one.

O.E. fyrst "foremost," superlative of fore, from P.Gmc. *furisto (cf. O.H.G. furist, O.N. fyrstr, Dan. første, M.Du. vorste "first," Ger. Fürst "prince"), superlative of *fur-/*for-, from PIE *pro- (cf. Av. pouruua- "first," fra- "forward, forth;" Skt. pūrva- "first," pra- "before, formerly," Gk. pro; L. pro; E. fore).

Naxost, from Mid.Pers. naxust "the first," Parthian Mid.Pers. nxwšt, from naxu, Manichean Parthian nwx "beginning" + -ist superlative suffix, Av. -išta-, cf. Skt. -istha-, Gk. -istos, O.H.G. -isto, -osto, O.E. -st, -est, -ost; naxostin, from naxost + suffix -in.
Yekom, from yek, → one, + -om suffix of ordinal numbers.
Âqâz "beginning," from Proto-Iranian *āgāza-, from prefix ā- + *gāz- "to take, receive," cf. Sogdian āγāz "beginning, start," pcγz "reception, taking."

first approximation
  نزدین ِ نخست   
nazdin-e naxost

Fr.: première approximation   

1) Generally, an expression to indicate that a comment or result is only approximate.
2) Math.: In calculus, limiting a differential equation to its → first derivative, for example: ex≅ 1 + x. Also called → linear approximation.

first; → approximation.

first collapse
  رمبش ِ نخست   
rombeš-e naxost

Fr.: premier effondrement   

An early phase in the process of star formation which begins when the mass of a → molecular cloud → clump exceeds the → Jeans mass. The collapse is initially → optically thin to the thermal emission from → dust grains, and the compressional heating rate is much smaller than the cooling rate by the → thermal radiation. The collapse proceeds → isothermally. The isothermal condition is broken when the central density reaches about 10-13 g cm-3 and a small region at the center of the cloud starts to become → opaque. The heat generated by the collapse in this region is no longer freely radiated away, and the compression becomes approximately → adiabatic. The central temperature and pressure then begin to rise rapidly, soon becoming sufficient to decelerate and stop the collapse at the center. There then arises a small central core, called the → first core, in which the material has stopped collapsing and is approaching → hydrostatic equilibrium. Outside this core, the material is still nearly isothermal and continues to fall inward almost in → free fall. Consequently a shock front arises at the boundary of the core, where the infalling material is suddenly stopped. The initial mass and radius of the core are about 1031 g and 6 x 1013 cm, respectively, and the central density and temperature are about 2 x 10-10 g cm-3 and 170 K, respectively. As the collapse proceeds, the core grows in mass due to the infall of the surrounding material; at the same time, however, the core radius decreases because of radiative energy losses from the outer layers of the core. The process leads to the → second collapse (R. B. Larson, 1969, MNRAS 145, 271).

first; → collapse.

first contact
  پرماس ِ نخست   
parmâs-e naxost

Fr.: premier contact   

1) The beginning of a → solar eclipse when the eastern part of the lunar limb touches the western limb of the Sun, marking the beginning of an eclipse.
2) For a → lunar eclipse, the moment when the eastern limb of the Moon is the first to enter the Earth's shadow.

first; → contact.

first core
  مغزه‌ی ِ نخست   
maqze-ye naxost

Fr.: premier cœur   

A first object in → hydrostatic equilibrium predicted to form during early dynamical contraction of a → molecular cloud → clump in the course of the → first collapse.

first; → core.

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