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

A unidirectional electric current that flows and ceases to flow at irregular or regular intervals.

→ intermittent; → current.

A Force acting between molecules.

→ inter-; → molecular; → force.

The determinant of a → Jacobian matrix formed by the n² → partial derivative s of n functions of n variables.

→ Jacobian; → determinant.

Logic: In a → syllogism, the → predicate of the → conclusion which occurs in the → major premise.

→ major; → term.

In → syllogism, the term which is common to both → premises and is excluded from the → conclusion.

→ mean; → term.

Logic: In a → syllogism, the categorical term occurring in both the → major term and the → minor term.

→ middle; → term.

Logic: In a → syllogism, the → subject of the → conclusion.

→ minor; → term.

In perturbation theory used in celestial mechanics, a term that indicates a bounded disturbance which recurs regularly. → secular term.

→ periodic; → term.

In perturbation theory used in celestial mechanics, a steadily increasing disturbance. → periodic term.

→ secular; → term.

The second term of the right-hand side in the → induction equation. This term is at the origin of the → dynamo effect and also of the → Alfven waves when in the presence of a mean field.

→ stretch; → term.

1) A word or group of words that has a precise meaning and expresses a definite idea, used in a particular science, art, or profession. See also → terminology; → determine.
2) Math.: In an expression, a number or a letter standing alone; or a combination of such representing a unit, e.g.: a, b, 5, 4ab, 3a/b.
3) Physics: A set of atomic states having a definite → configuration and → spin and → orbital angular momentum  → quantum numbers. In the → LS coupling scheme, the entity ^2S+1L_J, in which 2S+1 is called the → multiplicity of the term.
4) Logic: The → subject or → predicate of a → categorical proposition. See also → syllogism.
5) In → first-order logic, an → individual constant, → individual variable, or → function.

M.E. terme, from O.Fr., from L. terminus "boundary, limit, end; boundary stone or marker," variant termen "boundary, end;" cognate with Gk. termon "limit, boundary;" Skt. tarman "the top of the sacrificial (usually tripod) post; passage;" Irish tearmann "a refuge, sanctuary, asylum;" this Irish word would point to the sacredness of the sacrificial post in primitive IE customs; Hittite tarma- "peg, plug, nail;" PIE base *ter- "to cross;" cf. Pers. tarm, târem, tarâ-, Av. tar- "to cross over," as below.

Tarm, variant târem "boundary, limit," more specifically "a wooden palisade to exclude people from a garden," also "a wooden building of a circular form with an arched roof" (cf. Irish tearmann, as above), Tabari talm "pole, stick" (that marks a boundary), Tâleši/Tâti talmi "pole, stick," Garkâni taram "lever," Lori, Laki tarm "poles fastened together in order to carry a corpse to the village cemetery;" O.Pers./Av. tar- "to cross over," O.Pers. vi-tar- "to go across," Mid.Pers. vitartan "to pass," Mod.Pers. gozar, gozaštan "to pass, cross;" cf. Skt. tarman "the top of the sacrificial post; passage," tar- "to pass (through), overcome," tárati "crosses, passes," tirás "through, across, beyond;" see also → trans-.

1) Forming or found at the extreme point or limit of something, or relating to the very end of something.
2) Computers: An input/output device having a keyboard for communicating with a computer and usually a display.

M.E., from L. terminalis "pertaining to a boundary or end, final," from terminus "end, boundary line," → term.

Pâyâni, pâyâné, noun and adj. from pâyân "end, extremity; limit, boundary," from pâ(y) "foot; step" (Mid.Pers. pâd, pây; Av. pad- "foot;" cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; P.Gmc. *fot; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-).

The locus of stars on the → Hertzsprung-Russell diagram that are at the point of exhausting hydrogen in their cores. TAMS forms the upper luminosity boundary of the → main sequence strip. See also → zero age main sequence (ZAMS).

→ terminal; → age; → main; → sequence.

1) The constant maximum velocity reached by a body falling under gravity through a liquid or gas, especially the atmosphere. The body ceases to accelerate downward because the force of gravity is equal to the opposing force of resistance by the medium.
2) The velocity acquired at the end of a body's motion.
3) The velocity attained by → stellar wind at very large distance from the star. The material that escapes from the outer layers of the stars is accelerated outward from a small radial velocity at the → photosphere of the star, to some high velocity at large distance from the star. The theory of → radiation-driven winds predicts that the terminal velocity scales with the → escape velocity as: v_∞  ≅ 2-3 v_esc. The winds of hot → O stars experience fast acceleration and reach 80% of their terminal velocity near the star (some 3 R_*). The terminal velocity ranges from about 10 km s^-1 for a cool → supergiant star to 3000 km s^-1 for a luminous hot star. Terminal velocities are quite accurately measured from the violet trough of saturated → P Cygni line profiles in the ultraviolet (mainly N V λ1239, C IV λ1548, Si IV λ1394).

→ terminal; → velocity.

A → shock wave inside the → heliopause where the → supersonic → solar wind abruptly slows from an average speed of 500 km s^-1 to → subsonic and becomes denser and hotter.

Termination, verbal noun from terminate, from → term; → shock.

Toš, šok, → shock; pâyâni, → terminal.

The dividing line between the illuminated and the un-illuminated part of the Moon's or a planet's disk.

From L. terminator, from terminare, from terminus→ term.

Šid-marz, literally "light boundary," from šid "light, sunlight" (Mid.Pers. šêt "shining, radiant, bright;" Av. xšaēta- "shining, brilliant, splendid, excellent") + marz "boundary, limit" (Mid.Pers. marz "boundary;" Av. marəza- "border, district," marəz- "to rub, wipe;" Mod.Pers. parmâs "contact, touching" (→ contact), mâl-, mâlidan "to rub;" PIE base *merg- "boundary, border;" cf. L. margo "edge" (Fr. marge "margin"); P.Gmc. *marko; Ger. Mark; E. mark, margin).

1) The system of terms belonging to a particular science, art, specialized subject, or social group. Terminology is the way of naming concepts, which generally precede the corresponding terms. See also → lexicology.
2) The theory or science dealing with the relations between → terms and → concepts.

A hybrid word coined first in Fr., before 1764, by Yves Marie André (1675-1764), a Jesuit mathematician and philosopher, from termin, from L. terminus, → term, + epenthetic vowel -o- + Gk. -logia, → -logy. Recoined or borrowed in Ger. Terminologie in 1786, by C.G. Schütz of Jena; first appeared in E. in 1801.

From tarm, → term, + -šenâsi, → -logy.

1) Not definitely or authoritatively decided or settled.
2) Not known.

→ un-; → determined.