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

Optics: A strip or annulus of material, such as glass or film, whose density increases progressively from one end to the other. The function of the wedge is to weaken the light beam in an optical system.

Verbal adj. from → absorb; → wedge.

1) General: The process or fact of absorbing.
2) Physics: The action of energy or matter penetrating or being assimilated into a body of matter with no reflection or emission. → adsorption, → desorption, → sorption.
See also: → absorption band, → absorption coefficient, → absorption curve, → absorption feature, → absorption line, → absorption nebula, → absorption spectrum, → atmospheric absorption, → discrete absorption component, → foreground absorption, → intergalactic absorption, → internal absorption, → interstellar absorption, → mass absorption coefficient, → photoabsorption, → selective absorption, → self-absorption.

Verbal noun of → absorb; → -tion, from L. absorptionem.

1) A series of very closely spaced absorption lines in stellar spectra resulting from the absorption of light by molecules. Bands caused by titanium oxide (→ TiO bands) and carbon compounds occur in the spectra of low temperature M and C stars.
2) A range of wavelengths, usually in electromagnetic radiation, that are absorbed by a given substance. Absorption bands are characteristic of molecules and correspond to changes of electron orbits in the molecules. See also → anomalous dispersion.

→ absorption; → band.

The fraction of normally incident light that is absorbed per unit path length or by a unit mass of absorbing medium.

→ absorption; → coefficient.

A graphic representation of the amount of radiant energy absorbed by a material as a function of the wavelength.

→ absorption; → curve.

A dip in a spectrum indicating that light has been absorbed on the path from the emitting source to the observer. It may be a line, corresponding to a well-defined atomic or molecular transition, or a more complex feature whose physical origin is not necessarily understood.

→ absorption; → feature.

A dark line in the spectrum of a source produced by a lower temperature gas cloud lying between the source and the observer.

→ absorption; → line.

A dark cloud of dust and gas that absorbs light from and impedes the view of background stars; dark nebula.

→ absorption; → nebula.

A spectrum of absorption lines or bands, produced when light from a hot source, itself producing a continuous spectrum, passes through a cooler gas.

→ absorption; → spectrum.

The ratio of energy absorbed by a body to energy incident upon the same body.

Absorptivity, from absorptive adj. from → absorb + → -ity, suffix expressing state or condition.

Daršamâyi, from daršamâ quality adj. from daršam, present stem of daršamidan + -yi noun suffix.

For a spatial object, the ratio between its absorption of solar radiation and its infrared emission.

→ absorptivity; → emissivity; → ratio.

To keep oneself from doing or partaking of something; refrain. → avoid.

M.E. absteynen, absteinen, abstenen, from O.Fr. abstiner, abstenir, astenir "hold (oneself) back, refrain voluntarily," from L. abstinere / abstenere "withhold, keep back," from → ab-"off, away from" + tenere "to hold," from PIE root *ten- "to stretch," → tension.

Parhiz, from Mid.Pers. pahrêzidan, pahrêxtan "to keep away from, abstain," ultimately from Proto-Ir. *pati-raic-, from prefix *pati- + *raic- "to leave, let abandon;" cf. Av. raēc- "to leave, let;" Pers. (+ *ui-) gorêz-, goriz-, gorixtan "to run away, flee;" Skt. rec- "to leave, release;" Gk. leipo "I let;" L. linquô "I leave;" PIE base *leik^w- "to leave, let."

The act or practice of abstaining from indulging a desire or appetite.

Verbal noun of → abstain.

1a) (adj.) A designation of what derives from → abstraction. Contrasted to → concrete.
1b) Dissociated from any concrete reality or specific instance.
2a) (n.) An abstract thing or state.
2b) A summary of a scientific article, document, speech, etc.

M.E., from L. abstractus "drawn away," p.p. of abstrahere "to draw away, withdraw," from abs- "away," from → ab- + trahere "to draw," → attract.

1) Âhanjidé, p.p. of âhanjidan, variants âhixtan, âxtan "to draw, pull, extract," → object.
2) Cekidé, literally "dropped, oozed out," from cekidan "to drop, distill, fall in small portions, as water," from cek, cekké "a drop, as water," probably an onomatopoeia.

An entity that does not exist in space or time and is not perceptible. Some examples are universals, sets, geometrical figures, and numbers.

→ abstract; → object.

1) The mental process in which an element or quality is separated from a total object. Also the result of this process.
2) Chemistry: → abstraction reaction.

Verbal noun from → abstract; → -tion.

Chemistry: A bimolecular chemical reaction that involves removal of an atom or ion from a molecule. For example, hydrogen abstraction from methane: CH₄ + Cl → CH₃ + HCl.

→ abstraction; → reaction.

Ridiculously senseless, illogical, or untrue; contrary to all reason. → reductio ad absurdum, → absurdity. See also → nonsense.

M.Fr. absurde, from L. absurdus "out of tune; foolish," from surdus "deaf, stupid, inaudible."

Yâvé, literally "unrelated speech," ultimately from *ui-vaka-, from *ui- "apart, away," → transit, + *vaka- "word, speech," → word.

The quality or state of being absurd; something that is absurd.

→ absurd + → -ity.

1) The relative amount of a given → chemical element with respect to other elements.
2) The amount of an → isotope relative to other isotopes of the same element in a given sample. → overabundance; → underabundance.

M.E., from O.Fr. abundance, from L. abundantia "fullness," from abundare "to overflow," from L. → ab- "away" + undare "to surge," from unda "water, wave."

Farâvâni "abundance," from farâvân "abundant," from feré "much, more; increase; priority;" Mid.Pers. frêh "more, much;" O.Pers. fra- "before, forth;" Av. frā, fərrā "forth, forward;" PIE base *pro-; cf. L. pro "on behalf of, in place of, before, for;" Gk. pro- "before, in front of."