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

Same as → sound pressure.

→ acoustic; → pressure.

To press together; force into less space.

From O.Fr. compresser, from L. compressare "to press together," from comprimere "to squeeze," from → com- "together" + premere "to press;" PIE *prem-/*pres- "to strike."

Tanjidan "to squeeze, press, pull together," related to tang "tight," also "horse girth, a strap for fastening a load" (Mid.Pers. tang "tight, narrow"); cf. Skt. tanákti "draws together, contracts;" cognate with E. → tight; cp. Skt. tanákti "draws together, contracts;" M.H.G. dihte "dense, thick;" Ger. dicht "dense, tight;" O.H.G. gidigan; Ger. gediegen "genuine, solid, worthy;" PIE *tenk- "to thicken, clot; thick, solid."

Pressed into less space; condensed.

Past participle of → compress.

Air whose density is increased by being subjected to a pressure greater than atmospheric pressure.

→ compressed; → air.

The ability or quality to be reduced in volume. The coefficient of compressibility of a substance is given by c = (1/V).(δV/δp), where δV is the change in the volume resulting from a change of pressure δp, the temperature remaining constant.

Noun from → compressible.

Able to be reduced in volume. → compressible flow.

Adjective from → compress + -ible, variant of -able.

Tanjidani, tanješpazir from tanjidan, → compress, + adjective suffix -i; tanješpazir from tanješ, → compression, + pazir "receiving, admitting; having, endowed with;" → -able.

A flow in which changes of the density, induced by velocities and their fluctuations, are not negligible.

→ compressible; → flow.

The act or process of compressing; the state of being compressed.

Verbal noun from → compress.

In thermodynamics, the quantity Z = pV_m/RT, in which P is the gas pressure, V_m the molar volume, R the gas constant, and T the temperature. The compression factor is a measure of the deviation of a real gas from an ideal gas. For an ideal gas the compression factor is equal to 1.

→ compression; → facteur.

A → longitudinal wave that compresses the → medium along the direction of → propagation, such as a → sound wave. Same as → compressional wave.

→ compression; → wave.

Of or relating to → compression.

→ compression; → -al.

An → elastic wave that travels through a → medium with the particles of the medium moving in the same direction as the wave propagation. The compressional wave is the wave that is primarily used in → seismic exploration. Also called P-wave, primary wave, pressure wave.

→ compressional; → wave.

In → gamma ray → spectroscopy, a technique to reduce the contribution of gamma rays generated by → Compton scattering.

→ Compton; → suppression.

The repulsive interaction due to the → Coulomb energy between two ions. If the ionic charge is Z, then the Coulomb potential energy is Z²e²/a, where a is some typical separation between the ions. The Coulomb pressure is expected to become important when the ratio Γ_C = Z²e²/akT is much larger than 1. In that case, Coulomb effects dominate those of → thermal agitation and the gas settles down into a → crystal.

→ Coulomb; → pressure.

To cause to undergo → decompression.

→ de- + → compress.

1) A gradual decrease in surrounding → pressure, especially the controlled decrease in pressure that divers undergo after working in deep water or breathing compressed air.
2) Computers: The restoration of compressed electronic data to their full size.

→ de- + → compression.

Pressure in a degenerate electron or neutron gas. → degenerate matter.

→ degeneracy; → pressure.

1) Navigation:→ dip.
2) Meteorology: An area of low atmospheric pressure.
3) Geology: An area of the Earth's crust sunken or depressed below the surrounding area, formed by various mechanisms.

Depression, verbal noun of depress, from O.Fr. depresser, from L.L. depressare, frequentative of pressus, p.p. of deprimere "press down," from → de- "down" + premere "to press."

1) Našib-e ofoq, from našib "declivity, descent; lowness of ground, slope of any place" (Mid.Pers. nišēp "declivity, (astrology) dejection," Av. *nixšvaēpā-, xšvaēpā- "bottom, rear") + ofoq→ horizon. 2) Forubâr, from foru "down, downward; below; beneath," → de- + bâr "load, pressure, charge," → charge. 3) Našiblâx, from našib, as above, in item 1, + -lâx place suffix.

A property of a moving → fluid defined by (1/2)ρv² in → Bernoulli's law, where ρ is → density of fluid and v is → velocity. Dynamic pressure is the difference between → total pressure and → static pressure. Also called → velocity pressure. → ram pressure.

→ dynamic; → pressure.

1) To transform ideas into words; utter or state.
2) Math: To → transform into equivalent → terms. For example by → expanding or → factorizing an → expression. See also → suppress, → impress.

M.E. expressen, O.Fr. espresser "to press, squeeze out; speak one's mind," M.L. expressare, frequentative of exprimere "represent, describe," literally "to press out," from → ex- "out" + pressare "to press, push," from L. premere "to press, hold fast, cover, compress."

Zohâvidan, from zo- variant of os- "out," → ex-, + hâv, from Av. hau- "to press, squeeze out;" cf. Mid.Pers. hunîdan "to express, extract (juice)," hâwan "mortar;" akin to Skt. sav- "to press, press out;" O.H.G. sou, O.E. sēaw "juice;" + -idan infinitive suffix.