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: 3079 Search : on
dissolution
  والویش   
vâluyeš

Fr.: dissolution   

Chemistry: The process by which a solid, gas, or liquid is dispersed homogeneously in a gas, solid, or a liquid.

Verbal noun of → dissolve.

distance function
  کریای ِ اپست   
karyâ-ye apest

Fr.: fonction de distance   

Same as → metric.

distance + → function.

distance to the horizon
  اپست ِ افق   
apest-e ofoq

Fr.: distance à l'horizon   

The distance separating an observer and the → apparent horizon of the place. Neglecting the → atmospheric refraction, it is given by: d = (2Rh)1/2, where R is the radius of the Earth and h is the observer's height. This can be approximated to: d (km) = 3.57(h)1/2 for a typical value of R = 6378 km. The atmospheric refraction, however, makes the thing more complex, depending on the temperature and density variations along the line of sight. Generally, refraction pushes the apparent horizon about 10% farther.

distance; → horizon.

distinction
  بژنایش   
bažnâyeš

Fr.: distinction   

1) The act or an instance of distinguishing or differentiating.
2) A distinguishing feature.
3) The state of being different or distinguishable.
4) Special honor, recognition, or fame (The FreeDictionary.com).

distinct; → -tion.

distortion
  چولگی، چولش   
cowlegi (#), cowleš

Fr.: distorsion, déformation   

1) Extent to which a system, optical, acoustic, or electronic, fails to reproduce accurately at its output the characteristics of the input.
2) Optics: An optical imperfection caused by a → lens or → system of lenses which results in → magnification differences between different points on the → image. The points on the → object are misplaced in the image relative to the → center of the → field. See also → barrel distortion; → pincushion distortion.

Verbal noun of → distort.

distribution
  واباژش   
vâbâžeš (#)

Fr.: distribution   

An act or instance of distributing; the state or manner of being distributed; something that is distributed. → binomial distribution, → Bose-Einstein distribution, → brightness distribution, → chi-square distribution, → cumulative distribution function, → distribution function, → Gaussian distribution, → Gibbs canonical distribution, → lognormal distribution, → Maxwell-Boltzmann distribution, → normal distribution, → Poisson distribution, → power-law distribution, → probability distribution, → spectral energy distribution.

Verbal noun of → distribute

distribution function
  کریای ِ واباژش   
karyâ-ye vâbâžeš

Fr.: fonction de distribution   

A function that gives the relative frequency with which the value of a statistical variable may be expected to lie within any specified interval. For example, the Maxwellian distribution of velocities gives the number of particles, in different velocity intervals, in a unit volume.

distribution; → function.

diurnal aberration
  بیراهش ِ روزانه   
birâheš-e ruzâné

Fr.: aberration diurne   

The aberration of a star's position due to the rotation of the Earth. Its value depends on the latitude of the observer, and is only 0''.32 in the case of an observer at the equator, where the rotational velocity is greatest.

diurnal; → aberration.

diurnal libration
  هلازان ِ روزانه   
halâzân-e ruzâne

Fr.: libration diurne   

Daily geometrical libration of the Moon arising from the fact that observers at different points on the Earth see the Moon from slightly different angles. As the Moon rises in the east, you are positioned on one side of our planet, and by the time it sets in the west. Earth's rotation has carried you to the other side. This change in position produces a slight → parallax effect that adds about another 1° of libration in longitude. Two other geometrical libration are → libration in longitude and → libration in latitude. See also → physical libration.

diurnal; → libration.

diurnal motion
  جنبش ِ روزانه   
jonbeš-e ruzâné

Fr.: mouvement diurne   

The daily apparent motion of all celestial objects, due to Earth's rotation.

diurnal; → motion.

division
  ۱) بخش؛ ۲) شکاف   
1) baxš; 2) šekâf

Fr.: division   

1) The act or process of dividing; state of being divided.
Math.: An operation in which a dividend is divided by a divisor to give a quotient and a remainder.
2) Something that marks a division; a separation.

From O.Fr. division, from L. divisionem (nom. divisio), from divid-, stem of dividere "to cleave, distribute," from → dis- "apart" + -videre "to separate," from PIE base *widh- "to separate."

1) Baxš "portion, part, division," baxšidan "to divide, distribute, grant;" Mod./Mid.Pers. baxt "fortune, fate," baxtan, baxšidan "to distribute, divide," bâq "garden," initially "piece or patch of land," baq "god, lord;" Av. bag- "to attribute, allot, distribute," baxš- "to apportion, divide, give to," baxta- "what is allotted (luck, fortune)," baxədra- "part, portion," baγa- "master, god;" O.Pers. bāji- "tribute, tax;" cf. Skt. bhaj- "to share, divide, distribute, apportion," bhájati "divides," bhakta- "allotted; occupied with; a share; food or a meal, time of eating?" pitu-bháj- "enjoying food;" Gk. phagein"to eat (to have a share of food)"; PIE base *bhag- "to share out, apportion."
2) Šekâf "a fissure, crack, slit," šekâftan "to divide into two long strips, split, break," Mid.Pers. škâftan.

division sign
  نشانه‌ی ِ بخش   
nešâne-ye baxš

Fr.: signe de division   

A symbol placed between two quantities (dividend and the divisor) to indicate the division of the first by the second. The division sign is written as a horizontal line with dot above and dot below, ÷ (→ obelus), or a slash or horizontal line.

division; → sign.

documentation
  دپش   
dapeš

Fr.: documentation   

1) The use of documentary evidence.
2) A furnishing with documents, as to substantiate a claim or the data in a book or article.
3) Computers: Manuals, listings, diagrams, and other hard- or soft-copy written and graphic materials that describe the use, operation, maintenance, or design of software or hardware (Dictionary.com).

document; → -tion.

dodekatemorion
  دوازدهان   
davâzdahân (#)

Fr.: dodekatemorion   

A segment of the → zodiac extending 2.5 degrees, as considered in Babylonian and Hellenistic astrology; plural: dodekatemoria. Dodekatemoria result from a subdivision of each → zodiacal sign into twelve equal parts, each given the name of a → sign, beginning with the name of the sign being divided and continuing throughout the other eleven sequentially. Each zodiacal sign therefore contained a micro-zodiac within its own 30° span. Textual evidence for the micro-zodiac does not antedate the sixth century BC (F. Rochberg, 2010, In the Path of the Moon, BRILL).

From Gk. dodekatemorion "twelfth part," from dodekate "twelfth" (from dodeka "twelve") + morion "part."

Davâzdahân, from Mid.Pers. dwâzdahân "the twelve ones," from dwâzdah (Mod.Pers. davâzdah) "twelve;" Av. dvadasa, from dva "→ two" + dasa "→ ten."

domination
  چیرش   
cireš

Fr.: domination   

An act or instance of dominating.

Verbal noun of → dominate.

donor
  دهنده   
dahandé (#)

Fr.: donneur   

In a semiconductor, an impurity which may induce electric conduction by providing free electrons. → acceptor; → impurity.

M.E. donour, from O.Fr. doneur, from L. donator, from donare "to give as a gift," donum "gift," dare "to give," cognate with Pers. dâdan "to give," from PIE base *do- "to give."

Dahandé "giver," from dâdan "to give," Mid.Pers. dâdan "to give," O.Pers./Av. dā- "to give, grant, yield," Av. dadāiti "he gives," Skt. dadâti "he gives," Gk. didomi "I give," PIE base *do- "to give." For L. cognates see above.

donor star
  ستاره‌ی ِ دهنده   
setâre-ye dahandé

Fr.: étoile donneuse   

In a → binary system, a star whose gas is → accreted by a compact companion. The donor may be a → giant or a → supergiant with an enormously distended atmosphere and a significant → stellar wind, or a star filling its → Roche lobe in a → close binary.

donor; → star.

double refraction
  شکست ِ دوتایی   
šekast-e dotâyi

Fr.: double réfraction   

Formation of two refracted rays of light from a single incident ray; property of certain crystals, notably calcite.

double; → refraction.

double vision
  دوبینی   
dobini (#)

Fr.: vision double   

Same as → diplopia.

double; → vision.

double-diffusive convection
  همبز ِ دوپخشی   
hambaz-e do paxši

Fr.:   

An instability involving two layers of fluid with opposite gradients of properties. Same as → fingering instability. See also → salt finger. Double-diffusive instabilities commonly occur in any astrophysical fluid that is stable according to the → Ledoux criterion, as long as the entropy and chemical stratifications have opposing contributions to the dynamical stability of the system. They drive weak forms of convection, and can cause substantial heat and compositional → mixing. Two cases can be distinguished. In fingering convection, entropy is stably stratified (∇ - ∇ad < 0), but chemical composition is unstably stratified (∇μ < 0); it is often referred to as → thermohaline convection by analogy with the oceanographic context in which the instability was first discovered. In oscillatory double-diffusive convection, entropy is unstably stratified (∇ - ∇ad > 0), but chemical composition is stably stratified (∇μ > 0); it is related to semiconvection, but can occur even when the → opacity is independent of composition (P. Garaud, 2014, arXiv:1401.0928).

double;→ diffusive; → system.

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