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

A set of electrons with the same angular momentum quantum number, denote l. The number of electrons permitted in a subshell is equal to 2l + 1.

→ sub- + → shell.

The point of the surface of a celestial body (including the Earth) at which the Sun is directly overhead at a particular time.

→ sub-; → solar; → point.

Describing a speed that is less than the speed of sound in the medium concerned. → supersonic.

→ sub-; → sonic.

A flow in which the velocity of the constituting particles never exceeds that of sound in the same fluid. Also called subcritical flow.

→ subsonic; → flow.

1) That of which a thing consists; physical matter or material.
2) Physics: A species of matter, commonly homogeneous, that occurs in macroscopic amounts.
3) Philo.: That by virtue of which a thing has its determinate nature, which makes it what it is, as distinguished from something else.

M.E., from O.Fr. substance, from L. substantia "being, essence, material," from substans, pr.p. of substare "to stand under or be present," from → sub- "up to, under" + stare "to stand," cognate with Pers. istâdan "to stand," as below.

Zirist, literally "to stand under," from zir-, → sub-, + ist "to stand; to be standing, "from istâdan "to stand;" Mid.Pers. êstâtan; O.Pers./Av. sta- "to stand, stand still; set;" Av. hištaiti; cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand."

Grammar: A word or word group functioning syntactically as a noun. Substantives include nouns and → nominals.

M.E., from L.L. substantivus "of substance or being," from L. substantia "being, essence, material," → substance, contraction of "noun substantive" from L. nomen substantivum ("independent noun") as opposed to nomen adiectivum "noun adjective" ("dependent noun").

Ziristin, from zirist, → substance, + -in a suffix of relation.

1) Pertaining to a class of objects with a mass less than 8 percent that of the Sun.
2) → substellar point.

→ sub- + → stellar.

The mass limit below which → hydrogen fusion cannot take place, and the cloud collapse cannot lead to the formation of a star. The limit is 0.075 → solar masses, corresponding to about 80 Jupiter masses.

→ substellar; → limit.

An object with a mass too small to sustain the → proton-proton chain and thus become a true star. See → brown dwarf.

→ substellar; → object.

The point on the Earth, or other body, at which a particular star is directly overhead at a given time.

→ substellar; → point.

The fact or condition, for an object, of not being capable to sustain the → hydrogen fusion because of its low mass (less than 0.08 → solar masses).

→ substellar + → -ity.

A coherent component of a larger system.

→ sub-; → system

To be opposite and delimit the extent of an angle or side of a geometric figure.

From L. subtendere "to stretch beneath," from → sub- + tendere "to stretch," cognate with Pers. târ "string," tanidan "to weave," as below.

Zirtânidan from zir-, → sub-, + tânidan from tân "thread, warp of a web," tâl "thread" (Borujerdi dialect), târ "thread, warp, string," related to tur "net, fishing net, snare," from tanidan, tan- "to spin, twist, weave;" Mid.Pers. tanitan; Av. tan- "to stretch, extend;" cf. Skt. tan- to stretch, extend;" tanoti "stretches," tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch, as above; Lith. tiñklas "net, fishing net, snare," Latv. tikls "net;" PIE base *ten- "to stretch."

An angle whose two sides pass through the endpoints of an arc.

Subtended p.p. of → subtend; → angle.

The point on the surface of a celestial body where the star is perceived to be directly overhead (in zenith). The sublunar point and subsolar point are the equivalent points for the Moon and Sun, respectively.

→ sub-; → terrestrial.

Fine or delicate in meaning or intent.

M.E. sotil, from O.Fr. sotil, soutil, subtil "adept, adroit; cunning, wise; detailed," from L. subtilis "fine, thin, delicate, finely woven," from → sub- "under" + -tilis, from tela "web, net, warp of a fabric," → texture.

Naqz "subtle, elegant, beautiful, excellent, good."

To take one number away from another; deduct. To perform the arithmetic operation of → subtraction.

From L. subtractus, p.p. of subtrahere "to draw from beneath, take away, draw off," from → sub- "from under" + trahere "to pull, draw."

Zirkaršidan, literally "to draw beneath," from zir-, → sub-, + karšidan "to draw, pul, drag," variant of kašidan "to draw, protract, trail, drag, carry;" Av. karš- "to draw; to plow," karša- "furrow;" Proto-Iranian *kerš-/*xrah- "to draw, plow;" cf. Skt. kars-, kársati "to pull, drag, plow;" Gk. pelo, pelomai "to move, to bustle;" PIE base k^wels- "to plow."
Kâhidan, → decrease.

The operation of finding the difference between two numbers or quantities.

Verbal noun of → subtract.

1) Constituting or involving → subtraction.
2) Math.: Indicating or requiring subtraction; having a → minus sign.

→ subtract; → -ive.

Color produced by mixing pigments rather than light. Mixing all of the subtractive colors together results in the color black. See also → additive color.

→ subtractive; → color.