An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The slow motion of the → nodes of the Moon's orbit in the opposite direction to the Moon's movement. This westward motion, caused by perturbations of other bodies, mainly the Earth and Sun, has a rate of 19.35 degrees per year, making one rotation in 18.6 years.

→ regression; → node.

1) Evenly or uniformly arranged in space or time; orderly; well-ordered.
Math.: Of a polygon, having all sides and angles equal.
2) Conforming to some accepted rule, discipline, etc.

M.E. reguler, from M.Fr., from O.Fr. reguler, from L.L. regularis "continuing rules for guidance," from L. regula "rule," cognate with Pers. râst, → right.

1) Bâsâmân, from bâ- "with, having" (→ hypo- + sâmân "order, arrangement, disposition; boundary, limit," Lârestâni sâmon "sign or mark separating one field from another," Gilaki, Tabari šalmân "a straight peace of wood or beam, post;" Mid.Pers. sâmânak, sahmân "limit;" loaned into Arm. sahmân; cf. Skt. sīmān-, sīmā- "boundary, border, limit."
2) Razan-mand, from razan, → rule, + -mand a possession suffix.

A function of a complex variable which is single-valued in a domain and which has a finite derivative at every point.

→ regular; → function.

A galaxy which has a uniformly arranged, symmetrical morphology such as a spiral or elliptical galaxy. Opposite of → irregular galaxy.

→ regular; → galaxy.

The reflection of light when the reflecting surface is very smooth and the reflected rays bounce off parallel to each other. Opposite of → diffuse reflection; same as → specular reflection.

→ regular; → reflection.

A satellite that revolves around its planet in an equatorial orbit of low or moderate eccentricity close to the planet. One example of a regular satellite system is the Galilean satellites of Jupiter.

→ regular; → satellite.

To control, direct, or adjust by a rule, principle, method, etc.

From L.L. regulatus, p.p. of regulare "to control by rule, direct," from L. regula, cognate with Pers. râst→ right.

Razanidan, verbal form of razan, → rule, cognate with L. regula.

Controlled or governed according to a rule or principle or law.

Past participle of → regulate.

1) The act of regulating; the state of being regulated.
2) A law, rule, or other order prescribed by authority.
3) Electronics: The degree by which a voltage source is held near its no-load amplitude when a load is applied.

Verbal noun of → regulate.

A person or thing that regulates.
A governor mechanism for regulating the flow of fuel, steam, etc., to an engine in order to maintain constant speed under varying load or resistance.

Agent noun of → regulate.

The brightest star in the constellation → Leo (V = 1.35). Regulus is approximately 77.5 light-years from Earth. It is a triple star system composed of a hot, bluish-white star with a pair of small, faint companions. The main star (Regulus A) is a main sequence of type B7, with a luminosity 140 times brighter than the Sun. Its equatorial rotation speed being 317 kilometers per second, the fast rotation distorts Regulus into an oblate spheroid with an equatorial diameter about 30 percent larger than the polar diameter. As a result, the poles, with a temperature of 15,400 Kelvin, are much hotter than the equator, which glows at 10,200 Kelvin.

L., literally "little king," diminutive of rex "king," related to regere "to keep straight, guide, lead, rule," from PIE base *reg- "to rule, to lead straight, to put right;" akin to Pers. râst "right, straight, correct," → right.

Širdel, literally "the Lion's heart," on the model of Ar. Qalb al-Asad (قلب‌الاسد), from šir "lion;" Mid.Pers. šagr "lion" + del "heart;" Mid.Pers. dil; Av. zərəd- "heart;" cf. Skt. hrd-; Gk. kardia; L. cor Arm. sirt; PIE base *kerd- "heart;" O.E. heorte; E. heart; Ger. Herz; Bret. kreiz "middle."

1) The act or process of reionizing a gas; an instance of this action.
2) The → ionization of → neutral hydrogen atoms formed during → recombination epoch in the → early Universe. See also → reionization epoch.

→ re-; → ionize.

An early epoch in the → Universe's history, but after the → recombination epoch, when the → first stars formed and their → ultraviolet light began to ionize the → neutral hydrogen gas that filled the Universe. The epoch of reionization is estimated to last between → redshifts of 12 to 6 (or when the Universe had between 2 and 5% of its age). Reionization marks the end of the → Dark Age in cosmic history.

→ reionization; → epoch.

1) To become → ionized again.
2) To → ionize again.

→ re-; → ionize.

A type of electrically charged → black hole that is spherically symmetric and non-rotating. Another type of such objects is the → Kerr-Newman black hole.

Named after the German physicist Hans Jacob Reissner (1874-1967) in 1916 and the Finnish Gunnar Nordstrom (1881-1923) in 1918 independently worked out solutions different from those of Schwarzschild; → black hole.

To refuse to accept, take, consider, recognize, etc.

→ re- + jec-, combining form of jacere "to throw" + -tus p.p. suffix, → project.

1) (tr.) To find or show a connection between two or more people or things.
2) (intr.) To have a significant connection with or bearing on something.

From O.Fr. relater, from L. relatus literally "carried, brought back," from re- "back, again" + latus "carried, brought," used as p.p. of referre, from re- "back, again" + ferre "carry, bear," cognate with Pers. bordan "to carry, bear" (Mid.Pers. burdan, O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive)," Skt. bharati "he carries," Gk. pherein, L. fero "to carry;" PIE base *bher- "to carry").

Bâzânidan, literally "to bring, lead back," from bâz- "back, again," → re- + ân stem of ânidan "to bring; to lead; to guide," cf. dialectical Kurd. ânin "to bring, to lead to," Tâleši ânân, ânoe "to bring together two edges;" Mid.Pers. ônidan, nidan, nay- "to lead; to bring;" O.Pers. nay- "to lead; to bring" anaya "leads;" Av. nay- "to lead; to bring," naiieiti "leads;" cf. Skt. nī- "to lead," náyati "leads," aorist s. anait.

Connected; associated.

P.p. of → relate.

General: A connection or association between two or more things.
Math.: A property that associates two quantities in a definite order, as equality or inequality.

Verbal noun of → relate.

Same as → predicate symbol.

→ relation; → symbol.