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

An instrument composed of a vertical staff and a horizontal cross with a plumb line at the end of each arm. It was used in ancient Roman empire to survey straight lines, squares, and rectangles.

From L. groma, gruma, from Gk. → gnomon, possibly through Etruscan.

→ grating groove.

Groove, from O.N. grod "pit," or M.Du. groeve "furrow, ditch," from P.Gmc. *grobo (cf. O.H.G. gruoba "ditch," Goth. groba "pit, cave," O.E. græf "ditch"), related to grave (n.).

Šiyâr "furrow, ploughed ground," from Av. karši-, karša- "furrow," karšuiiā "plowed (land)," related to Mod.Pers. kašidan/kešidan "to carry, draw, protract, trail, drag;" Mid.Pers. kešidan "to draw, pull;" from Av. karš- "to draw; to plow;" cf. Skt. kars-, kársati "to pull, drag, plough," karṣū- "furrow, trench;" Gk. pelo, pelomai "to be in motion, to bustle;" PIE base k^wels- "to plow."

1) The surface of the Earth; soil.
2) The foundation or basis on which a belief or action rests.

From O.E. grund "foundation, ground, surface of the earth," from P.Gmc. *grundus (cf. Du. grond, Ger. Grund "ground, soil, bottom").

1) Zamin, variant zami "earth, ground," from Mid.Pers. zamig "earth;" Av. zam- "the earth;" cf. Skt. ksam; Gk. khthôn, khamai "on the ground;" L. homo "earthly being" and humus "the earth" (as in homo sapiens or homicide, humble, humus, exhume); PIE root *dh(e)ghom "earth."
2) Zaminé, from zamin + nuance suffix -é.

The lowest energy state of an atom, molecule, or ion, when all electrons are in their lowest possible energy levels, i.e. not excited.

→ ground; → state.

An astronomical observation carried out using a telescope on Earth, as opposed to that from an orbiting satellite.

→ ground; based, adj. of base, from O.Fr. bas, from L. basis "foundation," from Gk. basis "step, pedestal," from bainein "to step;" → observation.

Nepâheš, → observation; az "from," → ex-; zamin, → ground.

1a) Any collection or assemblage of persons or things considered together or regarded as belonging together; e.g. → Local Group of galaxies.
1b) Math.: A set of elements a, b, c, ..., finite or infinite in number, with a rule for combining any two of them to form a "product," subject to the following four axioms: → closure axiom, → associative axiom, → identity axiom, and → inverse axiom.
2a) (v.tr.) To place or associate together in a group.
2b) (v.intr.) To be part of a group.

From Fr. groupe "cluster, group," from It. gruppo "cluster, packet, knot," likely from P.Gmc. *kruppa "round mass, lump."

Goruh "group," from Mid.Pers. grôh "group, crowd."

A branch of mathematics concerned with structures called → groups and the description of their properties. Group theory provides a powerful formal method of analyzing abstract and physical systems in which → symmetry is present. It has a very considerable use in physics, especially → quantum mechanics, notably in analyzing the → eigenstates of energy of a physical system.

→ group; → theory.

The velocity at which the envelope of a → wave packet propagates, v_gr = dω/dk, at k₀ (the central value of k). The group velocity can be equal to, larger, or smaller than the → phase velocity.

→ group; → velocity.

The act or process of uniting into groups.
A collection of things assembled into a group.
The occurence of several astronomical objects, usually of the same category, in a region of the sky.

Verbal noun of → group.

To increase by natural development, as any living organism or part by assimilation of nutriment; increase in size or substance (Dictionary.com).

From M.E. growen, O.E. growan; cf. Du. groeien, O.H.G. grouwan; PIE base *ghre- "to grow, become green," from which is also derived grass.

Ruyidan, rostan "to grow," from Mid.Pers. rôditan, rustan "to grow;" Av. raod- "to grow, sprout, shoot," with fra- "to grow up, shoot forth;" cf. Skt. ruh- "to grow, develop, ascend, climb," rohati "grows," rudh- "to grow, sprout, shoot," rodhati "grows."

The act or process, or a manner of growing; development; gradual increase. → curve of growth; → grain growth.

Ruyeš, verbal noun of → grow; rost, past stem of ruyidan, → grow, used as verbal noun.

The Crane. A constellation in the Southern Hemisphere , located at 22h 30m right ascension, -45° declination. Its brightest star, of magnitude 1.7 and spectral type B7. Abbreviation: Gru; genitive: Gruis

From L. grus "crane;" akin to Gk. geranos "crane;" Welsh garan; Lith. garnys "heron, stork;" O.E. cran; E. crane. Named by Johann Bayer in 1603.

Dornâ "crane," from Turkish, a bird of the family Gruidae.

1a) An opinion that one reaches or to which one commits oneself on the basis of probability alone or in the absence of any evidence whatever.
1b) The act of forming such an opinion.
2a) To arrive at or commit oneself to an opinion about (something) without having sufficient evidence to support the opinion fully.
2b) To estimate or conjecture about correctly (Dictionary.com).

M.E. gessen, perhaps from Scandinavian; cf. Sw., Dan., Norw. gissa, M.L.G. gissen, M.Du. gessen, related to verb get.

Hads, from Ar. Hads "intuition, conjecture, surmise."

1) To → control or direct the → motion or course of.
2) Something that directs the motion or points the way. → autoguider, → guide star, → guider, → lightguide, → waveguide.

M.E. giden (v.), from O.Fr. guider "to guide, lead," from Frankish *witan "show the way" (cf. Ger. weisen "to show, point out," wissen "to know;" O.E. witan "to see"). Cognate with Pers. bin- "to see" (present stem of didan "to see"); Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" Skt. veda "I know;" Gk. oida "I know," idein "to see;" L. videre "to see;" PIE base *weid- "to know, to see."

Râh bordan "to guide, conduct," from râh "path, → way," + bordan "to carry, lead," → vector.

A relatively bright star conveniently located in the → field of view used for → guiding.

→ guide; → star.

Same as → guiding telescope.

A → technique used in astronomical → observations to keep the → telescope→ tracking in pace with the → rotational motion of the → Earth. Guiding consists of maintaining the → image of a star motionless during the observation. See also → guiding accuracy, → guiding telescope, → offset guiding, → autoguiding.

Verbal noun of → guide.

The accuracy (expressed in arcseconds) with which a → telescope follows the → rotational motion of the → Earth.

→ guiding; → accuracy.

In the → epicyclic theory of → galactic rotation, the center of the → epicycle.

→ guide; → center.

A telescope which is attached to a second telescope being used for photographic purposes. The guiding telescope, mounted parallel to the optical axis of the main telescope, is used by the observer to keep the image of a celestial body motionless on a photographic plate.

→ guiding; → telescope.