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

An advance printing, usually of an article in a periodical.

→ pre-; → print.

Relating to a stage or time prior to the rise of modern science and to the application of the → scientific method.

→ pre-; → scientific.

1) To lay down, in writing or otherwise, as a rule or a course of action to be followed; appoint, ordain, or enjoin.
2) Medicine: To designate or order the use of a medicine, remedy, treatment, etc. (Dictionary.com).

→ pre-; + scribe, → inscribe.

1) An act of prescribing.
2) A direction, usually written, by the physician to the pharmacist for the preparation and use of a medicine or remedy. The medicine prescribed (Dictionary.com).

Verbal noun of → prescribe; → -tion.

1) That prescribes; giving directions or injunctions.
2) Depending on or arising from effective legal prescription, as a right or title established by a long unchallenged tenure (Dictionary.com).

→ prescribe; → -ive.

The state or fact of being present.

Noun from → present.

1) Being, existing, or occurring at this time or now.
2) At this time; at hand; immediate.
3) Grammar: Noting an action or state occurring at the moment of speaking.

M.E., from O.Fr. present, from L. præsentem (nominative præsens) "present, immediate," from pr.p. of præesse "to be before, to be at hand," from præ- "before," → pre-, + esse "to be;" cf. Pers. ast "is," hastan, astan "to be;" O.P. ah- "to be," astiy "is;" Av. ah- "to be," astī "is;" Skt. as- "to be," ásti "is;" Gk. esti "is;" PIE base es- "to be."

Pišâst, on the model of L. præesse, as above, from piš, → pre-, + epenthetic -â- + ast "is," variants hast, hi, has (Qâyen), isâ (Rašt), a (Aftar), heye (Kurd.); Av./O.Pers. ah- "to be," Proto-Ir. *Hah- "to be," → existence.
Bâšandé agent noun from budan "to be;" → condition.
Konuni "presently," from konun, aknun "now, present," from *hak-nun, from *hak-, cf. Av. hakat- "at once, immediately" + nū- "now" (Mid/Mod.Pers. nun "now, at present"); Av. nūrəm "now;" O.Pers. nūram "now;" Skt. nú- "now, just, but," nūnám "now, at present, indeed;" Gk. nun "now;" L. nu- "now" (in nu-dis "the day after tomorrow"); Goth. nu "now;" O.E. nu; E. now; PIE base *nu- "now."

Same as → present epoch, → today, → current cosmological epoch.

→ present; → day.

Same as → present day, → today, → current cosmological epoch.

→ present; → epoch.

A → participle that indicates an ongoing action or state in the present.

→ present; → participle.

The present number of stars on the → main sequence per unit logarithmic mass interval per square parsec. The PDMF is the basis for deriving the → initial mass function (IMF). This mass function is not corrected for stellar evolution nor losses through stellar deaths.

→ present; → day; → mass; → function.

To occupy the place of authority or control, as in an assembly or meeting; act as president or chairperson (Dictionary.com).

→ pre-; → reside.

1) The highest executive officer of a modern republic, as the Chief Executive of the United States (often initial capital letter).
2) An officer appointed or elected to preside over an organized body of persons (Dictionary.com).

→ preside; → -ent.

Farneštgâr, from farnešt, present stem of farneštidan, → preside, + agent noun suffix -gâr, → -or, on the model of âmuzgâr "teacher."

Of or relating to an epoch earlier than the formation of the Sun.

→ pre-; → solar.

A → refractory → nanoparticle embedded in → meteorites and → interplanetary dust particles whose → isotopic ratios suggest formation earlier than the Solar System.

→ presolar; → grain.

A mathematical analysis, based on → self-similarity, used to predict the → mass function of spherically collapsing → dark matter halos. The formalism assumes that the fraction of mass in halos more massive than M is related to the fraction of the volume in which the smoothed initial density field is above some threshold δ_cρ, where ρ is the average density of the Universe, with the volume encompassing a mass larger than M. A variety of smoothing → window functions and thresholds have been argued, but the most common is a top-hat window in real space and δ_c≅ 1.69. The Press-Schechter formalism provides a relatively good fit to the results of numerical simulations in cold dark matter theories.

First described by William H. Press and Paul Schechter's paper (1974, ApJ 187, 425); → formalism.

The force per unit area.

M.E., from O.Fr. pressure, from L. pressura "action of pressing," from pressus, p.p. of premere "to press, compress."

Fešâr "squeezing, constriction, compression," verb fešordan, fešârdan "to press, squeeze;" phonetic variants Lori xošâr, Aftari xešâr, Qazvini, Qomi xošâl; cf. Khotanese ssarr- "to exhilarate;" loaned in Arm. ôšarak, in Ar. afšaraj "juice."

A broadening of spectral lines caused mainly by the stellar atmospheric density and the surface gravity of the star. The line strength of a spectral line depends on the number of atoms in the star's atmosphere capable of absorbing the wavelength in question. For a given temperature, the more atoms there are, the stronger and broader the spectral line appears. Denser stars with higher surface gravity will exhibit greater pressure broadening of spectral lines.

→ pressure; → broadening.

The pressure difference between two adjacent regions of a fluid that results in a force being exerted from the high pressure region toward the low pressure region.

→ pressure; → gradient.

A force resulting from → pressure gradient that is directed from high to low pressure.

→ pressure; → gradient; → force.