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

Optics: A measure of the convergence or divergence of a pair of light rays, defined as the reciprocal of the distance between the point of focus and a reference plane.
Ophthalmology: The turning motion of the eyeballs toward or away from each other.

back formation from → convergence and → divergence, ultimately from L. vergere "to turn, bend, be inclined;" cognate with Pers. gardidan "to turn, to change," → version.

Gerâyi, from gerâyidan "to incline toward; to intend; to make for." Gerâ may be a variant of Mod.Pers. kil "bent, inclined" (k/g and l/r interchanges), from PIE base *klei- "to lean, incline," cognate with L. clinare "to bend" (E. declination, inclination, etc.), Gk. klinein "to cause to slope, slant, incline," Skt. sri- "to lean," O.Pers. θray-, Av. sray- "to lean," P.Gmc. *khlinen (Ger. lehnen, E. lean).

In logical positivism philosophy, the claim that a statement is literally meaningful (it expresses a proposition) if and only if it either actually has been verified or could at least in principle be verified.

Quality noun from → verifiable; → principle.

That can be verified. → verify; → verification; → verifiability principle.

→ verify; → -able.

The act of verifying. The state of being verified.
The process of research and examination required to establish correctness, authenticity, or validity.

Verbal noun of → verify.

To ascertain the truth or correctness of, as by examination, research, or comparison.

M.E. verifien, from M.Fr. verifier, from M.L. verificare "to make true," from L. verus "true;" → -fy.

Râst-jostan, literally "to seek the truth, to seek the right," from râst "right, true; just, upright, straight" (Mid.Pers. râst "true, straight, direct;" Soghdian rəšt "right;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" PIE base *reg- "move in a straight line," hence, "to direct, rule") + jostan/juyidan "to seek, strive for" (Proto-Iranian *iud- "to struggle for something, to fight;" Av. yūδ- "to fight, struggle;" Mod.Pers. justan, juy- "to search, seek, ask for;" cf. Mid.Pers. vijuyihitan "to search, seek").

Of or pertaining to spring. → vernal equinox.

From L. vernalis "of the spring," from vernus "of spring," from uēr "spring," cognate with Pers. bahâr, as below.

Bahâri of or pertaining to bahâr "spring;" Mid.Pers. wahâr "spring;" O.Pers. vāhara- "spring time," θūra-vāhara- "name of a spring month;" Av. vaηhar "spring;" cf. Skt. vasara- "relating or appearing in the morning;" Gk. ear "spring;" L. uēr "spring," vernus "of spring;" O.N. vār "spring;" Lith. vasara "summer;" O.C.S. vesna "spring."

The point of intersection between the ecliptic and the celestial equator at which the Sun passes from south to north of the celestial equator during its apparent annual motion. The instant of this event. It occurs on March 20, 21 or rarely 19. At the vernal equinox, as with the → autumnal equinox, night and day are equal in length world over. Several thousands years ago the vernal equinox was in Aries, but because of precession it has now slid west into Pisces. Right ascension and celestial longitude are measured from the vernal equinox. Also known as spring equinox. → First Point of Aries.

→ vernal; → equinox.

The intersection point between the → celestial equator and the → ecliptic from where the Sun apparently enters into the northern celestial hemisphere.

→ vernal; → point.

The time interval between two successive passages of the Sun, when the true longitude of the Sun is considered. In other words, the interval during which the Sun's true longitude increases by 360 degrees. Its mean length for the epoch J2000.0 is 365.24236460 real solar days (approximately 365.2424 days). The vernal-equinox year, on which the Iranian calender is based, should not be confused with → tropical year. See also: A concise review of the Iranian calendar. → Iranian calendar

→ vernal; → equinox; → year.

A small movable scale running parallel to the main graduated scale in certain measuring instruments, such as the → sextant, used to obtain a fractional reading of one of the divisions on the main scale. Also known as Vernier scale.

After the French mathematician Pierre Vernier (1580-1637), who invented the scale in 1631.

A particular form or variant of something.
An account of something, given from a specific point of view.

M.E., from M.Fr. version, from M.L. versionem (nominative versio) "a turning," from p.p. stem of L. vertere "to turn;" cognate with Pers. gardidan "to change," as below.

Gardâk, present stem of gardidan "to change, to turn" (Mid.Pers. vartitan "to change, to turn;" Av. varət- "to turn, revolve;" cf. Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend") + -âk noun suffix.

Plural form: vertices.
1) Astro.: A point in the → celestial sphere toward which or from which the common motion of a group of stars is directed.
2) Math.: The → point where two → sides of a → plane figure or an → angle  → intersect.
3) In → graph theory, any of the points of which graphs are formed. Same as → node.

From L. vertex "highest point," literally "the turning point," originally "whirlpool," from vertere "to turn," cognate with Pers. vartidan, gardidan, → version.

Târak, variant târ "top, vertex, head, the middle of the head;" cf. Sogd. târ "summit, forehead;" Yaghnobi tôr(k) "the back of the head;" Yazghulami tur "summit, head;" Proto-Ir. *starH- "to spread," → expand; PIE *ster- "spread, extend."

1) The apparent → direction of → gravity at the point of observation.
2) Being in a position or direction → perpendicular to the → plane of the → horizon. See also → normal.

Vertical, literally "of or at the vertex, directly overhead," from M.Fr. vertical, from L.L. verticalis "overhead," from L. vertex (genitive verticis) "highest point"

Hajin, from haj, variant hac "anything held vertical, erected in the manner of a spear" (Dehxodâ), may be from Proto-Ir. *hac- "to follow;" cf. Av. (+ *ā-) hac- "to stick to;" Mid.Pers. hâz- "to lead, guide;" → associate.

The greater circle on the celestial sphere which passes through → zenith, → nadir, and the star and whose plane is perpendicular to the plane of horizon. Same as → azimuth circle.

→ vertical; → circle.

In computer science, a scaling in which the processing power of the same node/system is increased by increasing/decreasing its resources (CPU, memory, etc.). See also → horizontal scaling.

→ vertical; → scaling.

Plural of → vertex.

→ vertex.

In a high degree. → Very Large Telescope (VLT); → very massive star; → very high frequencies (VHF).

M.E.; O.Fr verai "true;" L. verax (genitive veracis) "truthful," from verus "true."

Besyâr, from bas "many, much" (Mid.Pers. vas "many, much;" O.Pers. vasiy "at will, greatly, utterly;" Av. varəmi "I wish," vasô, vasə "at one's pleasure or will," from vas- "to will, desire, wish").

Radio frequencies in the range 30 to 300 mega Hz.

→ very; → high; → frequency.

A radio interferometer consisting of 27 antennas, each 25 m in diameter, in a Y-shaped configuration. It is located about 100 km west of Socorro, New Mexico, and is operated by the United States National Radio Astronomy Observatory. The VLA has the resolution of a single antenna 36 km wide and the sensitivity of a dish 130 m across.

→ very; → large; → array.

A network of ten 25-m radio telescopes for → very-long-baseline interferometry (VLBI), operated by the U.S. National Radio Astronomy Observatory. Eight of the VLBA telescopes are distributed across the continental United States, while the other two are in Hawaii and the Virgin Islands, giving a maximum baseline of about 8,000 km and a resolution better than a milliarcsecond at its shortest wavelength.

→ very; → large; → baseline; → array.