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

1) The action, fact, or instance of occurring.
2) Something that happens; event; incident (Dictionary.com). 3) Logic: → bound occurrence; → free occurrence.

Verbal noun of → occur.

The intercommunicating body of salt water occupying the depressions of the Earth's surface, or one of its major primary subdivisions, bounded by the continents, or the equator, and other imaginary lines. A sea is subdivision of an ocean. the vast body of salt water that covers almost three fourths of the earth's surface.

M.E. ocean(e), from O.Fr. occean, from L. oceanus, from Gk. okeanos "the great river or sea surrounding the disk of the Earth, as opposed to the Mediterranean," of unknown origin. Personified as Oceanus, son of Uranus and Gaia and husband of Tethys.

Oqyânus, from Ar., ultimately from Gk., as above.

A hypothetical → exoplanet covered by a water envelope. The presence of such a planet stems from the implicit assumption of → Habitable Zone temperatures and a liquid water surface.

→ ocean; → planet.

Of, living in, or produced by the ocean.

→ ocean; → -ic.

That part of the → Earth's crust underling most of the Earth's surface which is covered by the oceans. It has a remarkably uniform composition (mostly ~ 49% SiO₂) and thickness (mostly ~ 7 km). The ocean floor is the most dynamic part of the Earth's surface. As a result, no part of the oceanic crust existing today is more than 200 million years old, which is less than 5% of the age of the Earth itself. New oceanic crust is constantly being generated from the → upper mantle by sea-floor spreading at → mid-ocean ridges, while other parts of the oceanic crust are being recycled back into the mantle at subduction zones.

→ oceanic; → crust.

Any section of the narrow, continuous submarine mountain chain through all the world's oceans. The oceanic ridge constitutes the most extensive mountain ridge on Earth, more than 65,000 km. Perhaps the best-known part of the ridge system is the → Mid-Atlantic Ridge.

→ oceanic; → ridge.

The study of the ocean, embracing and integrating all knowledge pertaining to the ocean's physical boundaries, the chemistry and physics of sea water, and marine biology.

→ ocean + → -graphy.

Oqyânus→ ocean + -šenâsi→ -logy.

Any of various natural clays rich in ferric oxides (Fe₂O₃) and containing silica and alumina. Used as a red (→ hematite) or yellow (→ limonite) pigment.

M.E. oker, O.Fr. ocre, from L. ochra, from Gk. okhra, from okhros "pale yellow."

Oxrâ, loan from Gk.

The notion that any hypothesis should be stripped of all unnecessary assumptions. If two hypotheses fit the observations equally well, the one that makes the fewest assumptions should be chosen.

The doctrine was formulated by William of Ockham (c.1288-c.1347), an English Franciscan friar and scholastic philosopher. Razor from O.Fr. rasour "a razor," from raser "to scrape, shave."

Ostaré "razor," from sotordan "to shave, erase, remove;" Mid.Pers. ôstarak "removed, shaved," ôstârišn "wiping, shaving;" cf. Khotanese ustar- "to remove," Sogdian (prefixed *pari-) prtr- "to wipe off, dry up," from Proto-Iranian *us-tar- "to remove, wipe off."

A prefix meaning eight.

From L. octo, Gk. okto, cognate with Pers. hašt, as below. Skt. asta, Goth. ahtau, O.E. eahta (see eight).

Hašt "eight," from Mid.Pers. hašt, O.Pers.*aštahva- "eighth;" Av. ašta; cf. Skt. astā; Ossetic ast; (Buddhist) Sogdian 'št; Gk. okto, L. octo (Fr. huit; Sp. ocho); P.Gmc. *akhto(u) (O.E. eahta, æhta, E. eight, O.N. atta, Ger. acht, Goth. ahtau); PIE base *oktô(u).
Octa-, oct, loaned Gk. forms, as above.

A group of eight units or figures.
Chemistry: An element, atom, or group having a valence of eight.

From Gk. oktad- (stem oktás) "group of eight," from okt-→ oct- + -ad a prefix denoting a group or unit comprising a certain number, sometimes of years (e.g. dyad; triad).

A polygon having eight angles and eight sides.

From L. octagonos, from Gk. oktagononos "eight-angled," from okta-, → octa-, oct- "eight," + gonia "angle," related to gony "knee," L. genu "knee," cuneus "a wedge;" Av. žnu- "knee;" Mod.Pers. zânu "knee," Skt. janu- "knee," kona- "angle, corner;" PIE base *g(e)neu-, see below.

Haštbar "eight-sided," from hašt "eight," → octa-, oct- + bar "side; breadth; breast" (Mid.Pers. var "breast;" Av. vouru "wide, broad, extended" (vourucašāni- "looking far"), related to varah- "breast;" cf. Skt. urú- "wide, broad," úras- "breast;" Gk. eurus "wide, broad;" PIE base uer-, ueru-s"wide, broad"); haštguš, from hašt, → octa-, oct-, + guš "corner, angle," Mid.Pers. gošak "corner."

A geometric solid with eight sides.

→ octa-, oct-; → -hedron.

The Octant. A faint and obscure constellation, at 21h right ascension, 80° south declination, containing the south celestial pole. Its star Sigma Octantis is the closest naked-eye star to the pole, but it is so faint (magnitude 5.47) that it is practically useless as a polar star for navigation purposes. Abbreviation: Oct; Genitive: Octantis. It was introduced by the French astronomer Nicolas Louis de Lacaille (1713-1762).

From L.L. octans "eighth part of a circle," from → octa-, oct- + -ans, as in quadrans; → quadrant.

Haštakân, → octant.

1) A portion of a circle cut off by an arc and two radii at 45°, one-eighth of the area of a circle.
2) A instrument incorporating a telescope, the predecessor of the → sextant, used to measure angular distances, mainly in nautical astronomy. It spanned an angular range of 45°.

From L.L. octans "eighth part of a circle," from → octa-, oct- + -ans, as in quadrans; → quadrant.

Haštakân, from haštak "one-eigth," from hašt "eight" (Mid.Pers. hašt, O.Pers.*aštahva- "eighth;" Av. ašta; cf. Skt. astā; Ossetic ast; (Buddhist) Sogdian 'št; Gk. okto, L. octo (Fr. huit; Sp. ocho); P.Gmc. *akhto(u) (O.E. eahta, æhta, E. eight, O.N. atta, Ger. acht, Goth. ahtau); PIE base *oktô(u) + -ak, contraction of yak "one," (Mid.Pers. êwak (Proto-Iranian *aiua-ka-); O.Pers. aiva- "one, alone;" Av. aēuua- "one, alone" (cf. Skt. éka- "one, alone, single;" Gk. oios "alone, lonely;" L. unus "one;" E. one) + -ân nuance suffix.

The interval between two musical notes, the fundamental components of which have frequencies in the ratio two to one.

M.E., from O.Fr. otaves, from L. octava feminine of octavus, from → octa-, oct- + -avus adj. suffix.

Octâv, loan from Fr. as above.

General: A group or series of eight.
Chemistry: A stable group of eight electrons which constitutes the outer electron shell of an atom of an inert gas (except helium whose only electron shell contains two electrons).

From → oct-, octa- + -et, as in duet.

Haštâyé, from haštâ "eightfold" + (y)é nuance suffix, as in dotâyé, → doublet.

Eightfold; eight times as great.

L. octuplus, from octu- variant (before labials) of → oct- octa- + -plus "fold," from base of plicare "to fold, twist."

Haštâyi, from hašt "eight," → oct- octa- + -tâyi, from tâ "fold, plait, ply; piece, part," also a multiplicative suffix; Mid.Pers. tâg "piece, part."

A → multipole consisting of eight point charges. Octupole moments are much smaller than → quadrupole moments and very much smaller than → dipole moment.

→ oct-; → pole.

1) Of, pertaining to, or for the eyes.
2) Optics: An alternative term for → eyepiece.

From L. ocularis "of the eyes," from oculus "eye," from PIE base *ok^w- "to see;" cf; Av. aši- "(both) eyes;" E. → eye.

Cašmi, related to cašm "eye" (Mid.Pers. cašm, Av. cašman- "eye," ākas- "to look," from prefix ā- + Proto-Iranian *kas- "to look, appear," cf. Skt. cáksus- "seeing"); didgâni, related to didgân "eyes," plural of didé "eye," from 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").