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: 13116 Search : far
curvature
  خمیدگی   
xamidegi (#)

Fr.: courbure   

A measure of the amount by which a curve, a surface, or any other manifold deviates from a straight line, a plane, or a hyperplane. In particular, The reciprocal of the radius of the circle which most nearly approximates a curve at a given point.
See also:
curvature constant, → curvature of space-time, → field curvature, → primordial curvature perturbation.

From L. curvatura, from curvatus, p.p. of curvare "to bend," from curvus "curved," → curve.

Xamidegi, from xamidé "curved," from xamidag "curved" + noun suffix -i.

curvature constant
  پارامون ِ خمیدگی   
pârâmun-e xamidegi

Fr.: paramètre de courbure   

A parameter occurring in the → Friedmann equations of → general relativity describing the geometry of → space-time. A spatially → open Universe is defined by k = -1, a → closed Universe by k = + 1 and a → flat Universe by k = 0. See also the → Robertson-Walker metric. See also → curvature of space-time.

curvature; → parameter.

curvature of space-time
  خمیدگی ِ فضا-زمان   
xamidegi-ye fazâ-zamân (#)

Fr.: courbure de l'espace-temps   

According to → general relativity, → space-time is curved by the presence of → matter. The curvature is described in terms of → Riemann's geometry. In → cosmological models three types of curvature are considered: positive (spherical, → closed Universe), zero (Euclidean, → flat Universe), and negative (hyperbolic, → open Universe). See also → curvature constant.

curvature; → space-time.

curve
  خم   
xam (#)

Fr.: courbe   

A line that deviates from straightness in a smooth, continuous fashion. A line representing a variable on a graph.

From L. curvus "crooked, curved, bent;" cf. Av. skarəna- "round," Gk. kirkos, krikos "a ring;" PIE base *sker- "to turn, bend."

Xam, variant kamân "arc," Mid.Pers. kamân, probably from PIE *kamb- "to bend, crook," cf. Breton kamm "curved, bent."

curve fitting
  سز ِ خم، سزکرد ِ ~   
saz-e xam, sazkard-e ~

Fr.: ajustement de courbe   

Construction of mathematical functions whose graphs are curves that "best" approximate a given collection of data points.

curve; → fitting.

curve of growth
  خم ِ رویش   
xam-e ruyeš

Fr.: courbe de croissance   

A plot showing how the → equivalent width of an → absorption line, or the radiance of an → emission line, increases as a → function of the → number of → atoms that produce the line.

curve; → growth.

curved
  خمیده   
xamidé (#)

Fr.: courbé   

Not straight.

Adj. from → curve.

curvilinear
  خم‌خط   
xam-xatt

Fr.: curviligne   

Consisting of, represented by, or bound by curved lines. → rectilinear.

From → curve + → linear.

cusp
  تیزه   
tizé (#)

Fr.: cuspide   

1) General: Pointed end. A point of transition. → polar cusp.
2) Either point of a → crescent moon.
3) A steep power-law representing the number density of stars in the central region of a galaxy. Cusps are characteristic of low-mass ellipticals. They are thought to result from the gravitational attraction of a central → supermassive black hole.
4) A peaked concentration of dark matter in the center of galaxies, as predicted by the → cold dark matter (CDM) model of galaxy formation. See also → cusp problem.
5) Math: A tooth-like meeting of two branches of a curve, with sudden change of direction.

L. cuspis "point, spear, pointed end."

Tizé, noun from tiz "sharp, pointed," from Mid.Pers. tēz, tēž, tigr "sharp," O.Pers. tigra- "pointed," Av. taēža-, tighra- "pointed," Skt. taējas- "the sharp edge (of a knife), piercing (flame)", from tij- "to be sharp, to pierce," Gk. stizein "to prick, puncture," stigma "mark made by a pointed instrument," L. instigare "to goad," P.Gmc. *stik- "to pierce, prick, be sharp," O.H.G. stehhan, Ger. stechen "to prick," O.E. stician "to pierce, stab," E. stick "to pierce;" PIE *st(e)ig- "to stick; pointed".

cusp problem
  پراسه‌ی ِ تیزه   
parâse-ye tizé

Fr.: problème des cuspides   

A problem encountered by the → cold dark matter (CDM) model of galaxy formation. The numerical simulations with CDM predict a large concentration of dark matter in the center of galaxies, with a peaked density distribution, in contrast to the real, observed galaxies. See also: → angular momentum catastrophe; → missing dwarfs.

cusp; → problem.

cut
  بریدن   
boridan (#)

Fr.: couper   

To penetrate or divide something, as with a sharp-edged instrument.

M.E. cutten, kytten, kitten; O.E. *cyttan, cognate with O.Swed. kotta "to cut;" O.N. kuti "little knife," or from O.Fr. couteau "knife."

Boridan "to cut off;" Mid.Pers. brin-, britan, brinitan "to cut off," brin "cut, delimitation, determined;" Av. (pairi-) brī- "to shave, shear;" cf. Skt. bhrī- "to hurt, injure," bhrinanti "they hurt."

cutoff
  بره   
boré

Fr.: coupure   

1) A designated limit beyond which the passage of something must be stopped.
2) A device that cuts off a transmission of photons.

cut; → off.

Boré, from bor- present stem of boridan "to → cut" + noun suffix .

cutoff filter
  پالایه‌ی ِ بره   
pâlâye-ye boré

Fr.: filtre à coupure   

Filter rejecting all light with wavelengths on one side of the cutoff wavelength.

cutoff; → filter.

cutoff voltage
  ولتاژ ِ بره   
voltâž-e boré

Fr.: tension de coupure   

The electrode voltage which reduces the value of a dependent variable, e.g. anode current, to a specified low value.

cutoff; → voltage.

cutoff wavelength
  موج-طول ِ بره   
mowj-tul-e boré

Fr.: longueur d'onde de coupure   

Wavelength at which the transmittance of a filter, or the detectivity of a detector, has fallen to one-half its peak value.

cutoff; → wavelength.

cyanide
  سیانور   
siyânur (#)

Fr.: cyanure   

A chemical compound that contains the → cyano radical, -CN. Most cyanides are highly toxic.

cyano-; → -ide.

cyano radical
  رادیکال ِ سیانو   
râdikâl-e siyâno

Fr.: radical cyano   

A diatomic chemical radical composed of carbon and nitrogen atoms. The triple bonds of C to H leave one electron available, which makes the CN radical very reactive. Organic molecules with the -CN group are potential sources of → prebiotic amino acids. Same as the → CN molecule. The CN radical was first identified by Gay-Lussac, who in 1815 published an extensive study of the derivatives of prussic acid (→ hydrogen cyanide). He showed that the cyano radical remained intact throughout a series of chemical transformations. Also called cyanogen radical.

cyano-; → radical.

cyano-
  سیانو-   
siyâno- (#)

Fr.: cyano-   

1) A combining form meaning "blue, dark blue," used in the formation of compound words. Also cyan- before a vowel.
2) A combining form representing → cyanide in the formation of chemical compounds.

From Gk. kyanos "dark blue, lapis lazuli," because of its presence in the Prussian blue, Fe7(CN)18, a dye which was first accidentally made around 1706, by heating substances containing iron and carbon and nitrogen.

cyanogen
  سیانوژن   
siyânožen (#)

Fr.: cyanogène   

1) A colorless, very poisonous, flammable gas with a smell of bitter almonds. Chemical formula: C2N2. It was discovered by Louis Joseph Gay-Lussac (1778-1850) in 1848.
2) A univalent radical, CN, found in simple and complex cyanide compounds. CN exists in → interstellar medium and is one of the main molecules detected in → comets. It has energy levels at 113 and 227 GHz (2.6 and 1.3 mm wavelength) above the ground level.

cyano- + → -gen.

cyanogen band
  باند ِ سیانوژن   
bând-e siyânožen (#)

Fr.: bande de cyanogène   

An → absorption band of molecular origin characterizing the spectra of → late-type stars (G0 and later, e.g. → S star). → Cyanogen absorption is an important → luminosity criterion for → low-mass stars, and is more pronounced in → giant stars than in → dwarf stars of the same → spectral type.

cyanogen; → band.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc 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 coo Cor Cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp 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 fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>