An Etymological Dictionary of Astronomy and Astrophysics
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A combining form meaning "wet, moist, moisture," used in the formation of compound words: → hygrogram; → hygrograph; → hygrometer .

Hygro-, from Gk, combining form of hygros "wet, moist."

Nam "humidity, moisture" + -negâšt, → -gram. The first component nam, from Mid.Pers. nam, namb "moisture;" Av. napta- "moist," nabās-câ- "cloud," nabah- "sky;" cf. Skt. nábhas- "moisture, cloud, mist;" Gk. nephos "cloud, mass of clouds," nephele "cloud;" L. nebula "mist," nimbus "rainstorm, rain cloud;" O.H.G. nebul; Ger. Nebel "fog;" O.E. nifol "dark;" from PIE *nebh- "cloud, vapor, fog, moist, sky."

The graphical record made by a → hygrograph.

→ hygro- + → -gram.

An instrument that records the hygrometer's measure of water vapor.

→ hygro- + → -graph.

An instrument that measures the relative humidity of the air.

→ hygro- + → -meter.

A member of a class of equations of state used in some models concerned with the evolution of a hypothetical supermassive star. The supermassive star is assumed to consist of a → convective core, which obeys a → polytropic law, and an envelope, which contains most of the whole mass, and follows the hylotropic → equation of state. This equation is expressed by P = A ρ^4/3M^α, where A is a constant, ρ the density, M the mass, and α an index. First introduced by Mitchell C. Begelman (2010, MNRAS 402, 673).

From → hylotropic, on the model of → polytrope.

Physical chemistry: Describing a substance that is capable of undergoing a change in phase (as from a liquid to a gas), with no change in chemical composition. If the substance is hylotropic over a limited range of pressure and temperatures, it is a pure chemical substance. If it is hylotropic over all pressure and temperatures except the most extreme ones, it is a → chemical element. See also → hylotrope.

First suggested by Wilhelm Ostwald (1904, in Annalen der Naturphilosophie 3, 355), from Gk. hylo-, combining form of hyle "matter; wood," because of the dependence on the composition, + → -tropic.

Mâdegard, from mâdé, → matter, + gard, → -tropic.

Physical chemistry: The fact or condition of being → hylotropic.

→ hylotropic; → -tropy.

A prefix appearing in loanwords from Greek meaning:
1) "Over," like → super-, and sometimes implying:
2) "Excess higher than that denoted by super-;" e.g. → hypernova.

From Gk. hyper, preposition and adverb, "over, beyond, overmuch, above;" cognate with L. super- and Pers. abar-, as below.

1) 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."
2) hiper, loanword from Gk.

A two-branched open curve, a type of conic section, defined as the intersection between a right circular conical surface and a plane which cuts through both halves of the cone.

From Gk. hyperbole "excess, exaggeration" literally "a throwing beyond," from hyperballein "to throw over or beyond," from → hyper- "beyond" + bol-, nom. stem of ballein "to throw."

Hozluli, loanword from Ar.

Of or pertaining to a → hyperbola.

From hyperbol-, → hyperbola, + → -ic.

A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (e^x + e^-x).

→ hyperbolic; → cosine.

Any of the six functions sinh, cosh, tanh, coth, csch, and sech that are related to the → hyperbola in the same way the → trigonometric functions relate to the → circle. Many of the formulae satisfied by the hyperbolic functions are similar to corresponding formulae for the trigonometric functions, except for + and - signs. For example: cosh²x - sinh²x = 1. See also: → hyperbolic cosine, → hyperbolic sine. Hyperbolic functions were first introduced by the Swiss mathematician Johann Heinrich Lambert (1728-1777).

→ hyperbolic; → function.

An orbit that is an open curve whose ends get wider apart at any rate between that of an ellipse and a straight line. Some comets' orbits become hyperbolic through the gravitational influence of a planet the comet passes near.

→ hyperbolic; → orbit.

A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (e^x - e^-x).

→ hyperbolic; → sine.

A three-dimensional space whose geometry resembles that of a saddle-shaped surface and is said to have negative curvature.

→ hyperbolic; → space.

A surface or body obtained by rotating a hyperbola about its axis of symmetry.

Hyperboloid, from hyperbol(a) + → -oid a suffix meaning "resembling, like."

Hozlulivâr, from hozluli, → hyperbola, + -vâr a suffix of similarity.

Extremely fine or thin, especially of a → spectral line split into two or more very thin components. → hyperfine structure; → hyperfine transition.

→ hyper-, → fine structure.

In spectroscopy, the → splitting of a spectral line into a number of very thin components. It results from a small perturbation in the energy levels of atoms or molecules due to the magnetic dipole-dipole interaction arising from the interaction of the nuclear → magnetic moment with the → spin of the electron. It can be observed only at high spectral dispersion. → fine structure.

→ hyperfine; → structure.

An → atomic transition involving a → hyperfine structure.

→ hyperfine; → transition.

A system consisting of a dominant → spiral galaxy associated with → dwarf satellite galaxies and intergalactic matter. Examples in the → Local Group are our Galaxy and the → Andromeda galaxy.

→ hyper- + → galaxy.