An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 690

Fr.: dissocier   

General: To separate from association of any kind.

Verbal form of → dissociation.


Fr.: dissociation   

General: An act or instance of dissociating; the state of being dissociated.
Chemistry: Separation of a molecule into two or more fragments (atoms, ions, radicals) by the absorption of electromagnetic radiation or the action of collisional phenomena.

From → dis- + (as)sociation, → association.

dissociation energy
  کاروژ ِ واهزش   
kâruž-e vâhazeš

Fr.: énergie de dissociation   

Energy required to dissociate a molecule. → dissociate.

dissociation; → energy.


Fr.: dissociatif   

Of, relating to, or tending to produce → dissociation.

Adj. of → dissociate.

dissociative recombination
  بازمیازش ِ واهزشی   
bâzmiyâzeš-e vâhazeši

Fr.: recombinaison dissociative   

A process where a positive molecular ion recombines with an electron, and as a result it dissociates into two neutral products. For example, AB+ + e-→ A + B, where e- is an electron, AB+ is a diatomic or polyatomic molecular ion, and A and B are the neutral fragmentation products. Dissociative recombination is the dominant recombination process in planetary ionospheres and interstellar clouds.

dissociative; → recombination.


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.


Fr.: dissoudre   

To make a solution of, as by mixing with a liquid; pass into solution.

From L. dissolvere "to loosen up, break apart," from → dis- "apart" + solvere "to loose, loosen, untie," from PIE *se-lu-, from reflexive pronoun *swe- + base *leu- "to loosen, divide, cut apart" (cf. Gk. lyein "to loosen, release, untie," Skt. lunati "cuts, cuts off," lavitram "sickle," O.E. leosan "to lose," leas "loose."

Vâluyidan, infinitive from stem vâlu(y)-, from vâ-de- + lu, variant of Mod.Pers. las "loose," "slit, cut," luš "torn," lok "torn, piece," lâc "open, wide open" (→ analysis), from PIE *leu- "to loosen, divide, cut apart."


Fr.: dissymétrie   

Absence or lack of symmetry

From → dis- + → symmetry.

Nâhmâmuni, from nâ- "non, un-," → a- + hmâmunisymmetry.

distal ejecta
  اشاناک ِ دور   
ešânâk-e dur

Fr.: éjecta distaux   

Geology: Impact ejecta found at distances more than 5 crater radii from the rim of the source crater.

Distal, from dist(ant), → distance + → -al; → ejecta.

Ešânâk, → ejecta; dur, → distance.

  اپست، دورا، دوری   
apest, durâ (#), duri (#)

Fr.: distance   

1) The → separation/→ length in → space/→ time between two → things/→ events.
2) The state of being apart in space or time.
3) In cosmology three different distance definitions are used: → angular diameter distance, → proper motion distance, and → luminosity distance. In a → flat Universe these three approaches give the same result. However, in the → Robertson-Walker metric they give three different but related values. In particular, angular diameter distance has a maximum value; therefore an object that lies further away than a closer object can appear larger.
See also:
angular size distance, → apparent distance, → comoving distance, → cosmic distance scale, → cosmological distance, → distance function, → distance modulus, → distance to the horizon, → focal distance, → Hubble distance, → perihelion distance, → polar distance, → redshift-distance relation, → velocity-distance relation, → zenith distance.

M.E., from O.Fr. destance, from L. distantia "a standing apart," from distantem (nominative distans) "standing apart, separate, distant," pr.p. of distare "to stand apart," from → dis- "apart, off" + stare "to stand," (cf. Mod.Pers. istâdan "to stand," O.Pers./Av. sta- "to stand, stand still; set," Skt. sthâ- "to stand," Gk. histemi "put, place, weigh," stasis "a standing still").

Apest, literally "standing apart," from apa- prefix denoting "separation, away, off," → dis-, + est variant of ist, present stem of istâdan, to stand," as above;" cf. Choresmian bst "to stand apart," from *apa- + st- "to stand," → stand.
Durâ, duri, noun from dur "far, distant, remote," Mid.Pers. dur, O.Pers. dūra- "far (in time or space)," Av. dūra-, from dav- "to move away," cf. Skt. dūrá- "distant, far."

distance function
  کریای ِ اپست   
karyâ-ye apest

Fr.: fonction de distance   

Same as → metric.

distance + → function.

distance modulus
  پیمون ِ اپست   
peymun-e apest

Fr.: module de distance   

The difference between the → apparent magnitude (m) of a star or galaxy and its → absolute magnitude (M). It is given by m - M = 5 log d - 5, where d is the distance in → parsecs. For an object that is 10 pc away, the distance modulus is zero.

distance; → modulus.

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.

  چوله‌کردن، چولیدن   
cowlé kardan, cowlidan

Fr.: déformer, altérer   

To twist awry or out of shape; make crooked or deformed (

From L. distortus, p.p. of distorquere "to distort," from → dis-, + torquere "to twist."

Cowlé "distorted, crooked, bent," variants [Mo'in] kowlé, kal, kil, Lori cowel, Laki hoval, hol, Malâyeri caval, hol, Tabari, Aftari val, Mid.Pers. xwahl "bent, crooked;" PIE base *klei- "to lean, incline" from which is also derived Gk. klinein "to cause to slope, slant, incline," L. clinare "to bend," → declination.

  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.

vâbâžidan (#)

Fr.: distribuer   

1) ( To divide and dispense in portions; to disperse through a space or over an area.
2) (v.intr.) Math.: To be → distributive. → distribution.

Distribute, from L. distributus p.p. of distribute "deal out in portions," from → dis- + tribuere "to pay, assign, allot," from tribus "tribe."

Vâbâžidan, infinitive of vâbâž, from vâ-dis- + bâž "tribute, toll, impost," from Mid.Pers. bâj, bâž "tribute, tax," baxtan "to distribute," baxt "luck, fate," O.Pers. bāji- "tribute, tax," Av. bag- "to distribute, divide, allot," cf. Skt. bhaj- "to share, distribute, apportion," Gk. phagein "to eat (to have a share of food)"; PIE base *bhag- "to share out, apportion;" → division.

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.


Fr.: distributif   

Characterized by or relating to → distribution. → distributive law.

distibution; → -ive.

distributive law
  قانون ِ واباژش   
qânun-e vâbâžš

Fr.: loi distributive   

Math.: In multiplication, the principle that permits the multiplier to be applied separately to each term in the multiplicand: x(y + z) = xy + xz. → associative law; → commutative law.

distributive; → law.

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