An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 726
retrograde object
  بر‌آخت ِ پسرو   
barâxt-e pasrow

Fr.: objet rétrograde   

An object which has a retrograde orbit around its primary.

retrograde; → object.

retrograde orbit
  مدار ِ پسرفت   
madâr-e pasraft

Fr.: orbite rétrograde   

An orbit with an inclination between 90° and 270° such as those of some comets and small asteroids orbiting the Sun.

retrograde; → orbit.

Reuleaux triangle
  سه‌بر ِ رولو   
sebar-e Reuleaux

Fr.: triangle de Reuleaux   

A shape of constant width created using an equilateral triangle and three similar circles. The equilateral triangle lies in the first circle with a vertex coinciding with the center of the circle and the sides equal to the circle radius. The centers of the two other circles are located at the two other vertices. The Reuleaux triangle is the intersection of the three circles.

Named after Franz Reuleaux (1829-1905), a German engineer, specialist of analysis and design of mechines; → triangle.

  وارونش، واگردانی   
vâruneš, vâgardâni

Fr.: inversion, interversion   

An act or instance of reversing. The state of being reversed. → phase reversal.

From → reverse + → -al.

  وارون، واگرد   
vârun, vâgard (#)

Fr.: contraire, opposé   

Opposite or contrary in position, direction, order, etc.
Acting in a manner opposite or contrary to that which is usual. → invert = vârun (وارون).

M.E. revers from O.Fr. revers "reverse, cross," from L. reversus, p.p. of revertere "to turn back," from → re- "back" + vertere "to turn," cognate with Pers. gard "to turn," as below.

Vârun "inverse, upside down," from vâ- "back, backward, again, re-," variant of bâz-, from Mid.Pers. abâz-, apâc-, O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from," apaš [adv.] "toward the back;" cf. Skt. ápāñc "situated behind."
Vâgard, from vâ-, → re-, + gard present stem of gardidan, gaštan "to turn, to change" (Mid.Pers. vartitan; Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend").

reverse shock
  تش ِ واگرد   
toš-e vâgard

Fr.: choc en retour   

A → shock front in a → supernova remnant (SNR) arising from the interaction of the → supersonic  → forward shock wave with the → interstellar medium (ISM) material. The reverse shock forms as the high pressure gas behind the forward shock wave expands and pushes back on the stellar ejecta. Reverse shock propagates into ejecta, starting from outside.

reverse; → shock.

vâgaštpazir (#)

Fr.: réversible   

Capable of returning to an original condition. → reversible process.

reverse + → -able.

reversible process
  فراروند ِ واگشت‌پذیر   
farâravand-e vâgaštpazir (#)

Fr.: processus réversible   

Any physical process which can be performed in the reverse direction, the whole series of changes constituting the process being exactly reversed. → irreversible process.

reversible; → process.

reversing layer
  لایه‌ی ِ واگردان   
lâye-ye vâgardân (#)

Fr.: couche d'inversion   

A layer of relatively cool gas forming the lower part of the Sun's chromosphere, just above the photosphere, that gives rise to absorption lines in the Sun's spectrum.

Reversing verbal adj. of → reverse; → layer.

  ۱) بازدا؛ ۲) بازدا کردن   
1) bâzdâ; 2) bâzdâ kardan

Fr.: 1) revue; 2) faire une revue   

1a) A critical article or report.
1b) The process of going over a subject again in study in order to examine and summarize the facts.
2) To discuss a research subject in a critical review; write a critical report upon.

M.E., from O.Fr. reveue "a reviewing, review," from feminine p.p. of revoir "to see again, reexamine," from O.Fr. reveoir, from → re- + veoir, veeir "to see."

Bâzdâ, from bâz-, → re-, + root of didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen") + kardan "to do," → -or.

review talk
  سخنرانی ِ بازدایی   
soxanrâni-ye bâzdâyi

Fr.: papier de revue   

A talk that deals with a subject by examining, criticizing, and summarizing the facts.

review; → talk.

bâznegaristan (#)

Fr.: réviser   

To alter something already written or printed, in order to make corrections, improve, or update (

M.E., from M.Fr. reviser, from L. revisere "to look at again, look back on," frequentative of revidere, from → re- "again" + videre "to see," → vision.

Bâznegaristan, from bâz- "again," → re-, + negaristan "to look, observe," → theory.

bâznegari (#)

Fr.: révision   

the act or work of revising. a process of revising. a revised form or version, as of a book.

Verbal noun of → revise.


Fr.: reprise, remise en vigueur, renouveau   

1) An improvement in the condition, strength, or fortunes of someone or something.
2) A restoration to life or consciousness.
3) An instance of something becoming popular, active, or important again (

revive; → -al.

  ۱) باز-زیویدن؛ ۲) باز-زیواندن   
1) bâz-zividan; 2) bâz-zivândan

Fr.: ranimer, réanimer, faire renaître   

1a) Regain life, consciousness, or strength.
1b) Give new strength or energy to.
2a) Restore to life or consciousness (

Ultimately from L. revivere; → re-; → survive.


Fr.: révocation   

The act of revoking; annulment.

Verbal noun of → revoke.


Fr.: révoquer   

1) To take back or withdraw; annul, cancel, or reverse; rescind or repeal.
2) To bring or summon back (

M.E., from O.Fr. revoquer, from L. revocare "rescind, call back," from → re- "back," + vocare "to call," from vox, → voice.

Vâvacidan, from vâ-, → re-, + vacidan "to call," → convoke.

gardeš (#)

Fr.: révolution   

The movement of a celestial body which is in orbit around another. It is often measured as the → orbital period.

Verbal noun of → revolve.

gardidan (#)

Fr.: tourner   

To move in a an orbit around another object. Compare with → rotate.

M.E. revolven, from L. revolvere "to turn, roll back," from → re- "back, again" + volvere "to roll."

Gardidan variant gaštan "to turn, to change;" gardun "wheel; chariot;" (+ → ni-) navardidan, navard- "to twist; to fold; to stroll;" Mid.Pers. wardidan, walt- "to turn; twist;" Av. varət- "to turn, revolve;" cf. Skt. vart- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wert- "to turn, bend."

Reynolds number
  عدد ِ رینولدز   
adad-e Reynolds (#)

Fr.: nombre de Reynolds   

A dimensionless quantity that governs the conditions for hydrodynamic stability and the occurrence of turbulence in fluids. It is defined by the ratio, R, of the inertial force (ρ u2) and the viscous force (μ u / L), i.e. R = L u ρ/μ, where L is a typical dimension of the system, u is a measure of the velocities that prevail, ρ the density, and μ the kinematic viscosity. At low Reynolds numbers the flow is steady, since the viscous forces are predominant in controlling the flow. At a critical value of R, corresponding to a critical velocity, the flow becomes turbulent.

Named after Osborne Reynolds (1842-1912), a British physicist who pioneered the study of turbulent flows; → number.

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