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

A line joining points of equal elevation or on a surface or points of equal intensity in a map.

→ contour; → line.

The spectral → emission line through which the → colling process takes place.

→ cooling; → line.

An → emission line in the spectrum of the → solar corona caused by highly ionized metal ions; especially those of iron, such as the red and green lines at 6375 Å and 5303 Å [Fe X] (Fe⁹⁺ ion) and [Fe XIV] (Fe¹³⁺ ion), respectively. From their discovery in 1870 until 1939, it was believed that these → forbidden lines would be due to an unknown element, called → coronium. Ultraviolet and X-ray coronal lines are also detectable in stars.

→ coronal; → line.

1) Of or like crystal; clear; transparent.
2) Formed by → crystallization.
3) Composed of crystals.
4) Pertaining to crystals or their formation (Dictionary.com).

Adjective from → crystal.

A → doubly convex, → transparent body in the → eye, situated behind the → iris, that focuses incident light on the → retina (Dictionary.com).

→ crystalline; → lens; → eye.

An arrangement and interrelationship of parts that is of → crystalline nature.

→ crystalline; → structure.

Consisting of, represented by, or bound by curved lines. → rectilinear.

From → curve + → linear.

One of the pair of yellow lines in emission spectra of neutral sodium (Na I). D1 has a wavelength of 5895.94 Å and D2 is 5889.97 Å. This sodium doublet is one of the strongest absorption features in the spectra of late-type stars.

Labelled D in a sequence of alphabetical letters first used by Joseph von Fraunhofer to designate spectral features in the solar spectrum, → Fraunhofer line.

The → neutral → helium  → spectral line at 5876 Å.

D3, because of confusion with the sodium → D lines. When Joseph N. Lockyer first observed this line in the solar spectrum at the eclipse of 1868, helium was not yet isolated on Earth. Initially, this line was thought to be the third member of the D1 and D2 line family of sodium which lie in the same yellow part of the spectrum; → line.

The time by which something must be finished or submitted; the latest time for finishing something (Dictionary.com).

Historically, during the American Civil War, the term referred to a physical line or boundary beyond which prisoners were shot; → dead; → line.

Ruzband, literally "day lock, that which blocks date," from ruz, → day, + band, → bond; cf. Ger. Stichtag, Anmeldeschluss, Einsendeschluss and Fr. date de clôture.

1a) To bend down; slope downward; descend.
1b) Grammar: To → inflect according to the various cases of a noun, adjective, or pronoun.
2) The process of declining; a downward movement; gradual loss or deterioration.

M.E. declinen, from O.Fr. decliner "to sink, decline, degenerate, turn aside," from declinare "to turn away, inflect," from → de- + clinare "to bend," cf. Gk. klinein "to cause to slope, slant, incline," Skt. sri- "to lean," O.Pers. θray-, Av. sray- "to lean," Mod.Pers. kil "bent, inclined, slant," PIE base *klei- "to lean, incline" from which is also derived (Ger. lehnen, E. lean).

Vâkil, from prefix vâ- "away" + kil "bent, crooked, inclined" [Dehxodâ], Mid.Pers. xwahl "bent, crooked" (Mod.Pers. dialectal/colloquial variants kowleh, cowleh, cowl, caval, xohl, xohal, hol), cf. Skt. kûla- "slope, declivity;" PIE base *klei-, as above. → inclination

1) A branch of learning or instruction.
2) A system of rules for behavior, methods of practice, etc.

M.E., from M.Fr. discipline, descepline, from L. disciplina literally "teaching, instruction," from discipulus "pupil, student, follower," from dis- + cipere, combining form of capere "to take," → concept, + -ulus, → -ule.

Hâvešân, from hâveš "disciple, pupil," Mid.Pers. hâvišt "disciple, pupil;" Av. hāvišta- "disciple, pupil," + -ân a suffix denoting "group, order, system."

A → spectroscopic binary in which the → spectral lines of both stars are seen and the lines are alternatively double and single. Same as → SB2 binary. See also: → single-lined binary.

→ double; → line; → binary

A → double-lined spectroscopic binary whose → light curve is typical of an → eclipsing binary.

→ double; → line; → eclipsing; → binary.

Same as → double-lined binary.

→ double; → line; → spectroscopic; → binary.

A bright line in the electromagnetic spectrum of a radiating substance caused by emission at a particular wavelength.

→ emission; → line.

In any → triangle, the straight line on which always lie the → centroid, → circumcenter, and → orthocenter.

→ Euler; → line.

The line drawn in a coordinate plane connecting the approximate values of the solution of a → first-order differential equation.

→ Euler; → broken line.

A → spectral line whose → energy levels have a → fine structure. Examples are [C II] 157.7 μm (→ singly ionized carbon), [O III] 88 μm, and [Ne II] 12.8 μm.

→ fine; → structure; → line.

Same as → streamline.

→ flow; → line.