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

The reappearance of a celestial body after an eclipse, an occultation, or a transit; same as emersion. → ingress.

From L. egressus, from egredi "to go out," from → ex- "out" + -gredi, comb. form of gradi "to walk, go, step;" from PIE *ghredh- (cf. Lith. gridiju "to go, wander," O.C.S. gredo "to come").

Osgâm "going out," from os- "out," → ex-, + gâm "step, pace," Mid.Pers. gâm, O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes," Mod.Pers. âmadan "to come," Skt. gamati "goes," Gk. bainein "to go, walk, step," L. venire "to come," Tocharian A käm- "to come," O.H.G. queman "to come," E. come; PIE root *gwem- "to go, come."

In statistics, a regression method that establishes a linear relationship between two random variables.

→ linear; → regression.

For a ring inclined to the planet's equator, the points at which the ring crosses the equator (nodes) slowly move around the planet (regress) in a direction opposite to that of the ring's orbital motion. (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ nodal; → regression.

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.