An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 763

Fr.: rupture   

Forcible division into pieces of an object. → tidal disruption.

From L. disruptio "a breaking asunder," noun of action from p.p. stem of disrumpere "break apart, split, shatter, break to pieces," from → dis- "apart" + rumpere "to break."

Gosixt, past stem of gosixtan "to tear away, to beark off."


Fr.: disséquer   

1) To cut apart (an animal body, plant, etc.) to examine the structure, relation of parts, or the like.
2) To examine minutely part by part; analyze: to dissect an idea (

L. dissectus, p.p. of dissecare "to cut to pieces," from dissecare "cut in pieces," from → dis- "apart" + secare "to cut," → section.

Vâsekanjidan, from vâ- "apart," → dis-, + sekanjidan "to cut to pices," cognate with šekastan "to break," → section.


Fr.: dissection   

The act of dissecting.

dissect; → -tion.


Fr.: dissiper   

1) To scatter in various directions. To spend or use wastefully.
2) To cause to lose (energy, such as heat) irreversibly. See also: → dissipation, → dissipative.

From L. dissipatus, p.p. of dissipare "to disperse, squander," from → dis- "apart" + supare "to throw, scatter."

Eftâl, eftâleš, from eftâlidan "to disperse; to tear; to break," ultimately from Proto-Ir. *abi-tard-, from *tard- "to pierce, split;" cf. Skt. tard- "to split, pierce, open;" Lith. trandéti "to be eaten by moths or worms;" PIE base *terd- "to pierce" (Cheung 2007).

  افتال، افتالش   
eftâl, eftâleš

Fr.: dissipation   

The loss of energy over time by a → dynamical system, typically due to the action of → friction or → turbulence. The lost energy is converted into heat, raising the temperature of the system. See also: → Ohmic dissipation. → viscous dissipation.

Noun form of → dissipate.


Fr.: dissipatif   

Relating to → dissipation.

dissipate; → -ive.

dissipative system
  راژمان ِ افتالی   
râžmân-e eftâli

Fr.: système dissipatif   

A → dynamical system which undergoes energy → dissipation. Such a system gives rise to → irreversible processes, associated with a time-asymmetric evolution of observable quantities.

dissipative; → system.


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 four main distance definitions are used: → luminosity distance, → angular diameter distance, → comoving distance, and → light-travel distance. In a → flat Universe these four approaches give the same result for the present epoch for distances below 100 Mpc. In a non-flat Universe with the → Robertson-Walker metric they give different but related values.
See also:
apparent distance, → cosmic distance scale, → cosmological distance, → distance function, → distance modulus, → distance to the horizon, → focal distance, → Hubble distance, → perihelion distance, → polar distance, → proper distance, → redshift-distance relation, → velocity-distance relation, → zenith distance.

M.E., from O.Fr., 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.

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