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

The antiparticle of a proton, identical in mass and spin but of opposite (negative) charge.

From → anti- + → proton.

A mathematical expression, derived from the → Clausius-Clapeyron equation, of the relation between the vapor pressure and the temperature of pure substances. It shows that the logarithm of vapor pressure is linearly dependent on the reciprocal of → absolute temperature.

Named after Louis Charles Antoine (1825-?), a French marine engineer, who derived the equation; → equation.

Grammar: A word opposite in meaning to another.

From → anti- + (syn)onym, → synonym.

Pâdcem, from opâd-, → anti-, + cem, → meaning.

The point at which a binary star is furthest from its companion.

Apastron, from Gk. ap-, → apo- + astron "star."

Apâstâr, apâsetâré, from apâ-, → apo-, + stâr, setâré, → star.

The point in the orbit of a planet, or other object in the solar system, which is furthest from the Sun.

Aphelion, from L. aphelium, from Gk. → apo- + helios "sun," cognate with L. sol, Skt. surya, Av. hvar-, Mod.Pers. xor, hur, O.H.G. sunna, Ger. Sonne, E. sun; PIE *sawel- "sun".

Apâhur, from Pers. prefix apâ, → apo-, + hur "sun."

The distance between the → Sun and an → object in orbit around it when they are at their farthest approach.

→ perihelion; → distance.

The point in a lunar orbit that is farthest from the center of the Lune. Also apolune.

Apocynthion, from → apo- "away from, off" + cynthion, from Gk. Cynthia "goddess of the Moon."

Apâmah, apâmâh, from apâ, → apo-, + mah, mâh, → Moon.

1) Generally, any process suppressing the secondary maxima of a diffraction pattern, such as the faint rings around the Airy disk of an optical image. This allows the telescope to resolve finer details.
2) Over a telescope aperture, the use of a screen that progressively cuts down, from the center to the edge of the aperture, the amount of light transmitted, in order to reduce diffraction.
3) A mathematical treatment carried out on data received from an interferometer before the Fourier transformation is calculated to obtain the spectrum.

Apodization from v. apodize, → a- "negation prefix" + pod from Gk. podos "foot" (compare with Pers. pâ, see below) + -tion "noun forming suffix;" literally "removing feet," i.e. suppressing the secondary maxima at the side of the Airy spot.

Pâzodâyi "removing feet," from pâ "foot," Mid.Pers. pâd, pây , Av. pad-, Skt. pat, Gk. pos, gen. podos, L. pes, gen. pedis, PIE *pod-/*ped-. Zodâyi, n. from zodudan "to polish, clean," Mid.Pers. uzdâtan, Av. uzdâ-, from uz-, → ex-, + dâ- "make, create."

The point at which a celestial body is farthest from the center of a galaxy; opposite of → perigalacticon.

From → apo- "away from, off" + galacticon, → galaxy.

From apâ, → apo-, + kahkašân, → galaxy.

The → full Moon when our natural satellite is at its farthest position from the Earth. The difference in apparent size with respect to the → perigee full Moon represents a difference in distance of just under 50,000 km between → apogee and → perigee, given the Moon's average distance of about 385,000 km. Also called → full micro Moon.

→ apogee; → full; → moon.

The circle determined by the intersection of the heavens with a → cone whose → vertex is the → eye, and whose elements are tangent to lines of the Earth's surface. Same as → visible horizon. Assuming that there is no → atmospheric refraction, apparent horizon coincides with → geometric horizon. See also → sea horizon.

→ apparent; → horizon.

The moment when the center of the Sun crosses the meridian. Same as true noon.

→ apparent; → noon.

1) The position on the celestial sphere at which a heavenly body would be seen from the Earth at a particular time.
2) A position given by the coordinates calculated for a star, if it were seen from the Earth's centre, relative to the → real equator and the → real equinox, at a certain date. It includes the displacements from one heliocentric direction, given in a stellar catalogue, due to → precession, → nutation, → aberration, → proper motions, → annual parallax, and light gravitational deviation (M.S.: SDE).

→ apparent; → position.

A period during which a → planet, → asteroid, or → comet is observable, generally between two successive → conjunctions of the body with the Sun.

M.E. apparicioun, from O.Fr. apparition, from L.L. appritionem "an appearance," from L. apparitus, p.p. of apparere "to appear."

Padidâri, n. from → padidâr + -i; padidâreš, verbal n. from *padidâridan.

In psychology of education, the fundamental process in acquiring knowledge, and the part played by existing knowledge.

From Fr. aperception, from N.L. apperceptionem, from ap- variant of → ad- before p + → perception.

From prefix bar- "on, upon, up" (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") + âgerteš, → perception.

1) General: The act of applying to a particular purpose or use.
2) Computers: A program that performs a specific function for the user, as contrasted with an environment or operating system. Some examples are Microsoft Windows, Microsoft Word, and Adobe Photoshop. The word "application" is used because each program has a specific application for the user.

Verbal noun of → apply.

A software with a specific function, such as a word processor or game. Contrast with operating system software.

→ application; → software.

1) Anxiety or fear that something bad or unpleasant will happen.
2) Understanding; grasp.
3) The action of arresting someone (Oxford Dictionary, lexico.com).

Verbal noun of → apprehend.

1) General: A guess or estimate; nearness in space, position, degree.
2) Math., Physics: Result that is not quite exact, but is within the limits of accuracy required for a given purpose.

Approximation, verbal noun of → approximate.

Nazdineš, verbal noun of nazdinidan, → approximate.

→ Rotation of the → line of apsides in the plane of the orbit in the same direction as the → revolution of the → secondary body. The major axis of the Earth's orbit rotates by 11.6 arcseconds per year.

→ apsidal; → motion.