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

An → H II region located in the rich star fields of the → Sagittarius area of the Milky Way. Its distance from the Earth is between 5,000 and 6,000 → light-years and spans some 15 light-years in diameter. Its other designations are: Swan Nebula, Messier 17, and NGC 6618.

Omega, Gk. alphabet letter; → nebula.

Another name for → Mira.

Omicron, Gk. alphabet letter; Ceti, → Cetus.

A bright star of → apparent visual magnitude  V = 4.3 lying in the constellation → Lupus. Among its other designations: HD 130807, HR 5528, HIP 72683. It is an → early-type star of → spectral type B5 IV and a member of the → Scorpius-Centaurus association. Ο Lupi is in fact a → binary system whose components have an angular separation of 0.043 arcsec, corresponding to a physical separation of 5.3 → astronomical units, with a mass ratio of 0.91.

→ Bayer designation; Lupi, genitive of → Lupus.

All, universally.

L. omni-, combining form of omnis "all, every," of unknown origin.

Visp-, from Mid.Pers. visp- "all;" O.Pers. visa-, vispa- "all;" Av. vīspa- "all, every, entire, universal" (vīspô.ayāra- "lasting all the days," vīspô.vīδvah- "knowing everything, omniscient"); cf. Skt. vīśva- "all, every; whole, universal."

Having very great or unlimited power or authority.

→ omni-; → power.

Same as → ubiquitous.

→ omni-; → present.

Having infinite knowledge, awareness, understanding, or insight.

→ omni-; L. scient "knowing," → science.

Visp-, → omni-, dânâ "knowing, learned," → science; âgâh "aware," → look.

Adverb, used as prefix denoting "in, into, onto; toward; with continuous activity," etc.

O.E. on, variant of an "in, on, into," from P.Gmc. (cf. Du. aan, Ger. an, Goth. ana "on, upon"), from PIE base *ano "on" (cf. Av. ana "on," Gk. ana "on, upon," L. an-, O.C.S. na, Lith. nuo "down from").

Bar "on; up; upon; in; into; at; forth; with; near; before; according to" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over").
Dar- "in," from Mid.Pers. andar, → intra-.

The state when two or more devices are directly connected and are communicating efficiently.
Of computers, operating under the direct control of, or connected to, a main computer.

→ on; → line.

Preliminary reduction of observational data at a telescope simultaneously with their acquisition.

→ on-line; → reduction.

In comparison with → off-source observation, an observation which is concerned with the source itself.

→ on-; → dource; → observation.

An approximation in the treatment of photoionized → H II regions, whereby secondary ionizing photons are absorbed immediately very close to their site of emission. The secondary photons, produced by → radiative recombinations directly to the → ground states, are thus ignored with respect to the ionizing photons emitted by the → exciting star. The OTS approximation requires that the ionized gas be sufficiently dense so that secondary ionizing photons are very likely absorbed within the H II region.

→ on; → spot; → approximation.

Nazdineš, → approximation; dar "in," from Mid.Pers. andar, → intra-.

1) The smallest whole number, symbol 1; unity. The → multiplicative identity for real and complex numbers.
2) Being or amounting to a single unit or individual or entire thing, item, or object rather than two or more; a single.

O.E. an, from P.Gmc. *ainaz (cf. O.N. einn, Dan. een, O.Fris. an, Du. een, Ger. ein, Goth. ains), PIE base *oinos, cognate with Pers. yek, as below.

Yek "one, alone," from Mid.Pers. êwak, êv, yak, êk; cf. Baluci hivak "one, single" (Proto-Iranian *aiua-ka-); O.Pers. aiva- "one, alone;" Av. aēuua- "one, alone;" Skt. éka- "one, alone, single;" Gk. oios "alone, lonely;" L. unus "one;" E. one.

A hypothetical flow in which all the flow parameters may be expressed as functions of time and one space coordinate only. This single space coordinate is usually the distance measured along the center-line of some conduit in which the fluid is flowing (B. Massey, Mechanics of Fluids, Taylor & Francis, 2006).

→ one; → dimensional; → flow.

A → magnetohydrodynamics treatment in which the → plasma consists only of one particle species and moves with the bulk speed. The thermal motion of the particles is neglected and thus there is no motion of particles relative to each other.

→ one; → fluid; → magnetohydrodynamics.

A relationship between two distinct sets of elements such that every member of the first set can be paired with a unique element in the second set; and every member of the second set can be paired with a unique element in the first set. Two sets so related are said to be isomorphic.

→ one; → correspondence.

A plant, Allium cepa, of the amaryllis family, having an edible, succulent, pungent bulb (Dictionary.com).

M.E., from Anglo-French union, O.Fr. oignon "onion," from L. unio-, also "pearl," literally "one, unity;" sense connection is the successive layers of an onion.

Mid.Pers. payâz, payâc; cf. Sogd. piyâk "onion," Yidgha piq, Vakhi piûk, Yazghulami piyeq, Kurd. pivaz; maybe related to PIE *peuk- "to prick, to sting, to stab," because of its pungent taste; cf. Gk. peukos "sting, prick, cusp, peak."

An adverb meaning without others or anything further; alone; solely; exclusively. → if and only if.

M.E., from O.E. anlic, from ân, → one.

Ivâz, from Mid.Pers. êvâz/êvâc, from Proto-Iranian *aiua-ka-; cf. Pers. yek, → one.
Tanhâ "only," from Mid.Pers. tanihâ "alone," literally "by one person," from tan "body, person;" Av. tanu- "body, person;" cf. Skt. tanu- "body, person;" perhaps related to Proto-Iranian *tan-, PIE root *ten- "to extend, stretch," → tension.

1) Classical philosophy: That part of metaphysics which is concerned with the nature of existence or the essence of things.
2) Contemporary philosophy: The conceptions of existence in general, such as those dealt with in various versions of existentialism.
3) Informatics: A description of knowledge as a set of concepts within a domain and the relationships that can exist between those concepts. An ontology is designed for the purpose of enabling knowledge sharing and reuse.

From Mod.L. ontologia, from Gk. on (genitive ontos) "being" (pr.p. of einai "to be"), akin to L. esse "to be;" Pers. hastan, astan "to be," hasti "existence, being," as below; + -logia, → -logy.

Hasti-šenâsi, from hasti "existence," from hastan "to be," → entity, + -šenâsi, → -logy.

A huge theoretical cloud of → comets surrounding the Sun between about 50,000 and 100,000 → astronomical units and thought to be the reservoir of → long-period comets entering the inner solar system.

Named after Jan Hendrik Oort (1900-1992), a Dutch astronomer who proposed its existence in 1950. He also made major contributions to our knowledge of the structure and rotation of the Milky Way Galaxy; → cloud.