An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 740
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 variants gaštan "to turn, to change," dialectal gel, gelidan, gellidan "to turn;" 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.

RHB star
  ستاره‌ی ِ RHB   
setâre-ye RHB

Fr.: étoile RHB   

Same as → red horizontal branch star.

red; → horizontal; → branch; → star.

Reâ (#)

Fr.: Rhéa   

The second largest satellite of Saturn, also known as Saturn V. It has a diameter of 1530 km and orbits Saturn at a mean distance of 527,040 km in 4.518 days. Rhea is composed primarily of water ice with rock making up less than 1/3 of its mass. It was discovered by Cassini in 1672.

In Gk. mythology Rhea was the sister and wife of Cronus (Saturn) and the mother of Demeter, Hades (Pluto), Hera, Hestia, Poseidon (Neptune), and Zeus (Jupiter).

reniom (#)

Fr.: rhénium   

A metallic chemical element; symbol Re. Atomic number 75; atomic weight 186.207; melting point about 3,180°C; boiling point about 5,625°C. Rhenium is a very dense, high-melting, silver-white metal; specific gravity 21.02 at 20°C. Of the elements, only carbon and tungsten have higher melting points and only iridium, osmium, and platinum are more dense. It was discovered by x-ray spectroscopy in 1925 by the German chemists, Walter Noddack, Ida Tacke and Otto Berg.

The name derives from L. rhenus for "the Rhine river in Germany".

ravâné šenâsi (#)

Fr.: rhéologie   

A branch of physics dealing with the way matter flows and deforms.

From rheo- "flow, current, stream," from Gk. rheos "stream," cognate with Pers. rud "river," → Eridanus, + → -logy.

Ravâné, from ravân "flowing, running," pr.p. of raftan "to go, walk; to flow;" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack") + šenâsi, → -logy.


Fr.: rhéonome   

Relating to a constraint or system that contains time explicitly. For example, a pendulum with an extensible string of length l rheonomous, the condition of constraint is: x2 + y2 = l2(t), where l(t) is the length of the string at time t.

From Gk. rheo-, from rheos "a flowing, stream, current," → rheology, + -nomous, → -nomy.

Rho Cassiopeiae
ρ Kâsiopé

Fr.: Rho Cassiopée   

A → yellow hypergiant in the constellation Cassiopeia, classified as F8-G2 Ia0pe. Rho Cas is about 11,650 light-years away from Earth, yet can still be seen by the naked eye, as it is 550,000 times as luminous as the Sun. It is in fact one of the most luminous stars in our Galaxy. ρ Cas is also one of the only seven currently known yellow hypergiants in the Milky Way. It is variable and fluctuates around magnitude 5 but dimmed to 6th magnitude on 1946. Its last eruption happened in 2000-2001, during which the star ejected about 10 percent of a solar mass, dimmed by more than a full magnitude, and changed its spectral type from late F to early M. During this outburst, the star surface cooled from 7,000 to 4,000 K.

Rho, a Gk. letter of alphabet used in → Bayer designation; Cassiopeiae, genitive of → Cassiopeia.

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