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: 3079 Search : on
reddening function
  کریای ِ سرخش   
karyâ-ye sorxeš

Fr.: fonction de rougissement   

The normalized interstellar extinction at a given wavelength. It is defined by f(λ) = A(λ)/A(Hβ) - 1, where A(λ) is the extinction at the given wavelength and A(Hβ) the extinction at Hβ, with f(Hβ) = 0. It is used to → de-redden observed fluxes: I(λ)/I(Hβ) = F(λ)/F(Hβ).10c(Hβ).f(λ), where I represents the flux in the absence of extinction and F the observed flux affected by extinction, c(Hβ) being the → reddening coefficient.

reddening; → function.

redshift space distortion
  چولگی ِ فضای ِ سرخ-کیب   
cowlegi-ye fazâ-ye sorx-kib

Fr.: distorsion dûe aux vitesses particulières sur la ligne de visée   

The distortion observed in → redshift space of → galaxy clusters caused by peculiar velocities of the members (→ peculiar velocity). In a perfectly homogeneous → Friedmann-Lemaitre Universe the redshifts would accurately measure radial distances from the observer, and the mapping from real space to redshift space would simply be an identity. In an inhomogeneous Universe the peculiar velocities associated with any inhomogeneous structure will introduce a distortion in this mapping (N. Kaiser, 1987, MNRAS 227, 1). See also: → fingers of God, → Kaiser effect.

redshift; → space; → distortion;.

redshift-distance relation
  بازانش ِ سرخ‌کیب-دورا   
bâzâneš-e sorxkib-durâ

Fr.: relation décalage vers le rouge-distance   

The correlation, first established by E. Hubble, between the cosmological recession velocities of galaxies and their distances.

redshift; → distance; → relation.

reduced Planck constant
  پایای ِ پلانک ِ باز‌هازیده   
pâyâ-ye Planck-e bâzhâzidé

Fr.: constante de Planck réduite   

The → Planck constant divided by 2π and denoted ħ, pronounced h-bar. Also called the → Dirac constant.

Reduced, p.p. of → reduce; → Planck's constant.

reduced Planck's constant
  پایای ِ پلانک ِ باز‌هازیده   
pâyâ-ye Planck-e bâzhâzidé

Fr.: constante de Planck réduite   

reduced Planck constant.

reduced Planck constant.

reduction
  باز‌هازش   
bâzhâzeš

Fr.: réduction   

1) In → data processing, the transformation of data from a "raw" form to some usable form.
2) Chem.: The removal of → oxygen from a substance, or the addition of → hydrogen to it. The term is also used more generally to include any reaction in which an atom gains → electrons.

Verbal noun of → reduce.

reflection
  بازتاب   
bâztâb (#)

Fr.: réflexion   

The return of radiation after striking a surface, without change in wavelength. If the surface is smooth, reflection is regular, otherwise it is diffuse. → diffuse reflection; → specular reflection.

Verbal noun of → reflect.

reflection coefficient
  همگر ِ بازتاب   
hamgar-e bâztâb (#)

Fr.: coefficient de réflexion   

The ratio given by the → amplitude (or energy) of a reflected wave divided by the amplitude (or energy) of the incident wave.

reflection; → coefficient.

reflection factor
  کروند ِ بازتاب   
karvand-e bâztâb

Fr.: facteur de réflexion   

The ratio of total flux that is reflected from a surface to the incident flux. Also called reflectance, reflectivity.

reflection; → factor.

reflection nebula
  میغ ِ بازتابی   
miq-e bâztâbi

Fr.: nébuleuse par réflexion   

A type of nebula that is visible from its reflection of starlight. Bright stars near reflection nebulae emit light into the region that is reflected by the large amount of dust there. The size of the dust grains causes blue light to be reflected more efficiently than red light, so these reflection nebulae frequently appear blue in color.

reflection; → nebula.

refraction
  شکست   
šekast (#)

Fr.: réfraction   

1) Optics: The change of direction which a beam of light undergoes as it enters a medium of different → refractive index.
2) Acoustics: The change in direction in sound waves on reaching the boundary between two media.
3) Seismology: The bending of a seismic wave as it enters a material of different density.

From L.L. refractionem (nominative refractio) "a breaking up," from L. refractus, p.p. of refringere "to break up," from re- "back" + combining form of frangere "to break," from PIE base *bhreg- "to break" (cf. Goth. brikan, O.E. brecan "to break;" Lith. brasketi "crash, crack").

Šekast, past stem of šekastan "to break, split;" Mid.Pers. škastan "to break;" Av. scind-, scand "to beak, cleave;" Proto-Iranian *skand- "to break, cleave;" PIE sken- "to cut off."

refutation
  واکوتش   
vâkuteš

Fr.: réfutation   

The act or process of refuting.

refute; → -tion.

regeneration
  باز-آزانش   
bâz-âzâneš

Fr.: regénération   

1) Act of regenerating; state of being regenerated.
2) Electronics: A feedback process in which energy from the output of an amplifier is fed back to the grid circuit to reinforce the input.
3) Biology: The restoration or new growth by an organism of organs, tissues, etc., that have been lost, removed, or injured (Dictionary.com).

re-; → generation.

region
  ناحیه   
nâhiyé (#)

Fr.: région   

A large, usually continuous segment of a surface or space; area. → H II region.

M.E., from Anglo-Fr. regioun; O.Fr. region, from L. regionem (nominative regio) "district, country, direction, boundary," from regere "to direct," cognate with Pers. râst, → right.

Nâhiyé, loan from Ar. nâHiyat.

registration
  برنوسش   
barnuseš

Fr.: enregistrement   

1) The act or instance of registering.
2) An entry in a register (Dictionary.com).

register; → -tion.

regression
  ۱) پسرفت؛ ۲) وایازی، وایازش   
1) pasraft (#); 2) vâyâzi (#), vâyâzeš (#)

Fr.: régression   

1) Astro.: → retrograde motion.
2) Geology: A retreat of the sea from land areas. Possible causes include a drop in sea level or uplift.
3) Math.: A method for fitting a curve through a set of points using some goodness-of-fit criterion. The most common type of regression is → linear regression.

From L. regression-, from regress-, stem of regredi "to go back," from → re- "back" + gradi "to step, walk."

1) → retrograde.
2) On the model of → progression, from vâ-re- + yâzi, yâzeš, verbal noun of yâzidan "to stretch out the arms; grow up" (Parthian Mid.Pers. y'd "to reach a goal, come to, stretch out;" Av. yat- "to reach, take one's place," yaiiata "places," frā-iiatāt "has reached;" cf. Skt. yat- "to be in place, put in place, line up;" PIE base *iet- "to be in place").

regression analysis
  آنالس ِ وایازش   
anâlas-e vâyâzeš

Fr.: analyse de régression   

A statistical technique used to determine the values of parameters for a function that best fits a given set of data.

regression, → analysis.

regression coefficient
  همگر ِ وایازش   
hamgar-e vâyâzeš (#)

Fr.: coefficient de régression   

The slope of the straight line that most closely relates two correlated variables.

regression, → coefficient.

regression curve
  خم ِ وایازش   
xam-e vâyâzeš

Fr.: courbe de régression   

A curve representing a non-linear relationship between two or more → variables.

regression, → curve.

regression equation
  هموگش ِ وایازش   
hamugeš-e vâyâzeš

Fr.: équation de régression   

A mathematical expression that describes the relationship between two or more variables. It indicates the nature of the relationship and, in particular, the extent to which one can predict some variables by knowing others.

regression, → equation.

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