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

A small depression on the surface of a → meteorite, more particularly on iron meteorites. These indentations result from the erosion of areas on the → meteoroid as material is ablated on its passage through the atmosphere.

From N.L., from Gk. rhegma "fracture, break" + Gk. glypt combining form of glyphein "to hollow out, carve, engrave."

Câluk "small hole" (Tabari), from câl, câlé "hole," from câh "a well, pit" (Mid.Pers. câh "a well;" Av. cāt- "a well," from kan- "to dig," uskən- "to dig out" (O.Pers. kan- "to dig," akaniya- "it was dug;" Mod.Pers. kandan "to dig"); cf. Skt. khan- "to dig," khanati "he digs," kha- "cavity, hollow, cave, aperture") + -uk, variant -u, a suffix of diminutive or attribution.

1) The layer of rocky → debris and → dust that forms the uppermost surface of → planets, → natural satellites, and → asteroids. Regolith on Earth is a product of → weathering.
2) In particular, → lunar regolith.

From Gk. regho(s) "rug, blanket" + -lith, from lithos "stone."

Sangpuš, literally "stone, rock covering," from sang "→ stone, rock," + puš present stem of pušidan "to cover; to put on," → envelop.

1) Astro.: → retrograde motion.
2) Geology: A retreat of the sea from land areas. Possible causes include a drop in sea level or uplift.
3) Math.: A method for fitting a curve through a set of points using some goodness-of-fit criterion. The most common type of regression is → linear regression.

From L. regression-, from regress-, stem of regredi "to go back," from → re- "back" + gradi "to step, walk."

1) → retrograde.
2) On the model of → progression, from vâ-→ re- + yâzi, yâzeš, verbal noun of yâzidan "to stretch out the arms; grow up" (Parthian Mid.Pers. y'd "to reach a goal, come to, stretch out;" Av. yat- "to reach, take one's place," yaiiata "places," frā-iiatāt "has reached;" cf. Skt. yat- "to be in place, put in place, line up;" PIE base *iet- "to be in place").

A statistical technique used to determine the values of parameters for a function that best fits a given set of data.

→ regression, → analysis.

The slope of the straight line that most closely relates two correlated variables.

→ regression, → coefficient.

A curve representing a non-linear relationship between two or more → variables.

→ regression, → curve.

A mathematical expression that describes the relationship between two or more variables. It indicates the nature of the relationship and, in particular, the extent to which one can predict some variables by knowing others.

→ regression, → equation.

A mathematical function that describes the relationship between two or more variables in a set of data.

→ regression, → function.

The curve representing a → linear regression. It is a line drawn through a set of data that summarizes the relationship between the → variables being studied.

→ regression, → line.

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."