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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 12948 Search : far
cylindrical coordinates
  هماراهای ِ استوانه‌ای   
hamârâhâ-ye ostovâne-yi (#)

Fr.: coordonnées cylindriques   

A coordinate system for a point in space, using an origin (O) and three perpendicular axes (Ox, Oy, Oz), in which a point (P) in space is specified by three numbers ρ, φ, z. The two first numbers, ρ and φ, are → polar coordinates for the vertical projection of P on the xy-plane, and z is the vertical distance of P from the xy-plane.

cylindrical; → coordinate.

cylindrical lens
  عدسی ِ استوانه‌ای   
adasi-ye ostovâneyi (#)

Fr.: lentille cylindrique   

A lens in which at least one surface is formed like a portion of a cylinder. Also called astigmatic lens.

cylinder; → lens.

Cynthian
  ماهی، مانگی   
mâhi (#), mângi (#)

Fr.: cynthien   

Referring to the Moon.

From L. Cynthia "the Moon," from Gk. Kynthia "woman from Kynthos." Kynthos was the mountain on Delos on which she and her twin brother Apollo were born.

Mâhi, mângi referring to mâh, mâng, → moon.

Cytherean
  ناهیدی   
Nâhidi (#)

Fr.: cythérien   

Referring to the planet Venus.

From Cythera, in Gk. mythology another name of Aphrodite (Roman equivalent Venus), goddess of love and beauty, since she was believed to emerge from the Mediterranean island Cythera.

Nâhidi referring to Nâhid, planet Venus, Mid.Pers. Anahid "immaculate, unstained," goddess of pure waters and fertility, from Av. arədvi-sûra-anâhita, from arədvi- "increasing, rising," + sûra- "strong, powerful" (Skt. śūra- "valient, courageous") + anâhita "unstained," from an- negation prefix + âhita "spotted."

D line
  خط ِ D   
xatt-e D

Fr.: raie D   

One of the pair of yellow lines in emission spectra of neutral sodium (Na I). D1 has a wavelength of 5895.94 Å and D2 is 5889.97 Å. This sodium doublet is one of the strongest absorption features in the spectra of late-type stars.

Labelled D in a sequence of alphabetical letters first used by Joseph von Fraunhofer to designate spectral features in the solar spectrum, → Fraunhofer line.

D ring
  حلقه‌ی ِ D   
halqe-ye D

Fr.: anneau D   

The inner → Saturn's rings, with a width of 7,500 km, lying before the → C ring, at 66,900 km from the center of Saturn.

ring.

d'Alembert's paradox
  پارادخش ِ دالامبر   
pârâdaxš-e d'Alembert

Fr.: paradoxe de d'Alembert   

A hydrodynamical paradox arising from the neglect of → viscosity in the → steady flow of a fluid around a submerged solid body. According to this paradox, the submerged body would offer no resistance to the flow of an → inviscid fluid and the pressure on the surface of the body would be symmetrically distributed about the body. This paradox may be traced to the neglect of the viscous forces, which are indirectly responsible for fluid resistance by modifying the velocity field close to a solid body (Meteorology Glossary, American Meteorological Society).

d'Alembert's principle; → paradox.

d'Alembert's principle
  پروز ِ دالامبر   
parvaz-e d'Alembert

Fr.: principe de d'Alembert   

The statement that a moving body can be brought to a → static equilibrium by applying an imaginary inertia force of the same magnitude as that of the accelerating force but in the opposite direction. More specifically, when a body of mass m is moving with a uniform acceleration a under the action of an external force F, we can write: F = m . a, according to Newton's second law. This equation can also be written as: F - ma = 0. Therefore, by applying the force -ma, the body will be considered in equilibrium as the sum of all forces acting on it is zero. Such equilibrium is called → dynamic equilibrium. Owing to this principle, dynamical problems can be treated as if they were statical.

Named after the French mathematician and philosopher Jean le Rond d'Alembert (1717-1783), who introduced the principle in his Traité de dynamique (1743).

d'Alembert-Lagrange principle
  پروز ِ دالامبر-لاگرانژ   
parvaz-e d'Alembert-Lagrange

Fr.: principe d'Alembert-Lagrange   

d'Alembert's principle.

d'Alembert's principle; → Lagrangian.

d'Alembertian operator
  آپارگر ِ دالامبر   
âpârgar-e d'Alembert

Fr.: d'alembertien   

A second order, → partial differential operator in space-time, defined as: ▫2 = ∂2/∂x2 + ∂2/∂y2 + ∂2/∂z2 - (1/c2)∂2/∂t2, or ▫2 = ∇2 - (1/c2)(∂2/∂t2), where ∇2 is the → Laplacian and c is the → speed of light. This operator is the square of the → four-dimensional operator  ▫, which is Lorentz invariant.

d'Alembert's principle; → operator.

D-type ionization front
  پیشان ِ یونش ِ گونه‌ی ِ D   
pišân-e yoneš-e gune-ye D

Fr.: front d'ionisation de type D   

An → ionization front of → H II regions whose expansion speed is comparable to the → sound speed in the gas (~ 10 km/sec for hydrogen at 104 K). A D-type ionization front results from → R-type ionization front when its propagation speed decreases as the volume of gas ahead of the ionization front grows. If front velocity is equal to a lower limit (C12 / 2C2, where C1 and C2 are the sound speed ahead and behind the front respectively), the front is called D critical.

D referring to a dense gas; → type; → ionization; → front.

D3 line
  خط ِ D3   
xatt-e D3

Fr.: raie D3   

The → neutral → helium  → spectral line at 5876 Å.

D3, because of confusion with the sodium → D lines. When Joseph N. Lockyer first observed this line in the solar spectrum at the eclipse of 1868, helium was not yet isolated on Earth. Initially, this line was thought to be the third member of the D1 and D2 line family of sodium which lie in the same yellow part of the spectrum; → line.

DA white dwarf
  سفید‌کوتوله‌ی ِ DA   
sefid kutule-ye DA

Fr.: naine blanche DA   

A → white dwarf whose spectrum shows the → Balmer lines of hydrogen only, with no helium or metals.

D short for → dwarf; A a convention; → white.

Dalton minimum
  کمینه‌ی ِ دالتون   
kamine-ye Dalton

Fr.: minimum de Dalton   

A 40-year period of unusually low → solar activity, from about 1790 to 1830. See also the → Maunder minimum.

Named after John Dalton (1766-1844), British meteorologist; → minimum.

damping
  میرایی   
mirâyi (#)

Fr.: amortissement   

Of an oscillating system, the progressive decrease with time in the amplitude of the oscillation, due to friction (internal or external) or other resistance.

M.E. damp "black damp, a poison gas occurring in a mine," from Mid.Du. or Mid. Low German; akin to O.H.G. damph "vapor."

Mirâyi, noun from mirâ "getting extinguished, going out, expiring, dying," from mordan, present tense stem mir- "to die," Mid.Pers. murdan "to die," O.Pers. mrt- "to die," amriyta "dies," martiya- "(mortal) man" (Mod.Pers. mard "man"), Av. mərəta- "died," Skt. mar- "to die," mrti- "death;" PIE base *mor-/*mr- "to die." Cognates in other IE languages: Gk. emorten "died," ambrotos "immortal," L. morior "I die," mortuus "dead" (Fr. mourir "to die," mort "dead"), Arm. merani- "to die," O.C.S. mrutvu "dead," O.Ir. marb, Welsh marw "died," O.E. morþ "murder," Lith. mirtis "man."

dance
  ۱) وشت؛ ۲) وشتن، وشتیدن   
1) vašt (#); 2) vaštan (#), vaštidan

Fr.: 1) danse; 2) danser   

1a) A successive group of rhythmical steps or bodily motions, or both, usually executed to music.
1b) An act or round of dancing.
2a) To move one's feet or body, or both, rhythmically in a pattern of steps, especially to the accompaniment of music.
2b) To leap, skip, etc., as from excitement or emotion; move nimbly or quickly (Dictionary.com).

M.E. da(u)ncen "to dance," from O.Fr. dancier of unknown origin, perhaps related to O.H.G. *dansjan "to lead (someone) to a dance."

Vašt, variant of gašt, gardidan, gel, gelidan "to turn," → revolve, cf. Eastern Gilâni gilâr "dance."

dancer
  وشتار، وشتنده، وشتگر   
vaštâr, vaštande, vaštgar

Fr.: danseur, danseuse   

1) A person who dances.
2) A person who dances professionally, as on the stage (Dictionary.com).

dance; → -er.

Vaštâr, from vašt "dnace," + agent noun suffix -âr, as in parastâr, padidâr; vaštande, vaštgar with agent noun suffixes, -ande and -gar, → -or.

danger
  خطر   
xatar (#)

Fr.: danger   

1) Liability or exposure to harm or injury; risk; peril.
2) An instance or cause of peril; menace (Dictionary.com).

M.E. daunger, from O.Fr. dangier "power, power to harm, authority, control," alteration of dongier, from V.L. *dominarium "power of a lord," from L. dominus "lord, master," → domain.

Xatar "danger," loan from Ar.

Danjon astrolabe
  اسطرلاب ِ دانژون   
ostorlab-e Danjon

Fr.: astrolabe de Danjon   

A modern unportable astrolabe which is used for high precision measuring of stellar and geographical coordinates. The instrument uses the simultaneous observations of two images of the same star, one of the images formed directly by the lower face of a prism and the other by the light rays reflected first from a mercury bath and then by the upper face of the prism. The images coincide when the zenithal distance of the star attains a prefixed value (Gauss method of equal altitudes, → almucantar). Apart from astrometry, the Danjon astrolabe was used for studying the Earth's rotation and is currently used for solar radius measurements.

After André Danjon (1890-1967), French astronomer, who developed the instrument at the Strasbourg Observatory before the Second World War and at the Paris Observatory in 1948. The concept of prism astrolabe was initially invented by the French Auguste Claude (1858-1938) around 1900 and was later modified in collaboration with Ludovic Driencourt (1861-1940); → astrolabe.

Danjon scale
  مرپل ِ دانژون   
marpel-e danjon

Fr.: échelle de Danjon   

A scale to evaluate as exactly as possible the darkening degree of a total → lunar eclipse. The five steps of the scale run from 0 (extremely dark, invisible Moon) to 4 (extremely bright, the eclipse having a very weak effect on the Moon's visibility). The darkening at a lunar eclipse is determined to a great extent by the transparency of the terrestrial atmosphere, which is affected by clouds and the dust from the volcanic eruptions (M.S.: SDE).

Named after André Danjon, who set up the scale, → Danjon astrolabe; → scale.

<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir 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 coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>