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

(British: traveller) A person or thing that travels.

→ travel; → -er.

1) A tall, woody perennial plant usually with a single trunk.
2) Math.: → factor tree.
3) A → data structure that is used to represent hierarchical data.
4) In → graph theory, a → connected graph with no → cycles.
5) A mathematical structure that can be viewed as either a graph or as a data structure. Many powerful algorithms in computer science and software engineering are tree based algorithms.

M.E., from O.E. treo, treow "tree, wood," from P.Gmc. *trewan (cf. O.S. trio, O.N. tre, Goth. triu), from PIE *deru- "wood" (cf. Mod.Pers. dâr "tree;" O.Pers. dāruv- "wood;" Av. dāuru- "piece of wood, tree trunk;" Skt. dāru- "tree, wood;" Gk. drus "tree;" Serb. drvo "tree;" L. larix "larch tree;" Rus. drevo "tree, wood;" Pol. drwa "wood;" Lith. derva "pine wood;" O.Ir. daur, Welsh derwen "oak").

Deraxt "tree;" Mid.Pers. draxt "tree," two possible etymologies. A suffixed variant of dâr "tree," cognate with E. tree, as above. Alternatively, from Av. *draxta- "firmly stood, fixed" (as in handraxta-), from drang-, dranj- "to fix, fasten, strengthen, hold," dražaite "holds," infinitive drājnhe; cf. Khotanese drys- "to hold;" Sogdian drγ- "to hold;" Parthian Mid.Pers. drxs "to endure."

A type of → data structure in which each element is attached to one or more elements in a hierarchical manner. Trees are often called inverted trees because they are normally drawn with the root at the top.

→ tree; → structure.

A graphical representation that displays a hierarchical view of data.

→ tree; → view.

A general tendency, course, or direction.

From M.E. trenden "to roll about, turn, revolve," from O.E. trendan, (cf. O.E. trinde "round lump, ball," O.Fris. trind, M.L.G. trint "round," M.L.G. trent "ring, boundary," Du. trent "circumference," Dan. trind "round").

Ravâl, from row present stem of raftan "to go, walk, proceed" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack") + suffix -âl, → -al.

In medieval astronomy, a spurious oscillatory motion of the equinoxes thought to have a period of 7,000 years. This concept, attributed to Thâbit ibn Qurra (c. 830-901), had a profound influence on medieval astronomy. In order to explain trepidation, Thâbit was said to have added a new sphere to the eight Ptolemaic spheres beyond the sphere of fixed stars.

From L. trepidationem "agitation, trembling," from trepidare "to tremble, hurry," from trepidus "anxious, scared;" cf. Skt. trprá- "hasty;" PIE base *trep- "to shake, tremble."

Larzeš, verbal noun of larzidan "to tremble, shiver;" Mid.Pers. larzidan "to shake, tremble;" Manichean Mid.Pers. rarz- "to shiver with fever;" Proto-Iranian *rarz- "to shake, tremble."

1) Law: An unlawful act causing injury to the person, property, or rights of another, committed with force or violence, actual or implied. → light trespass.
2) To commit a transgression or offense; transgress; offend; sin (Dictionary.com).

M.E. trespas, from O.Fr. trespasser "pass beyond or across, cross, traverse; infringe, violate," from tres- "beyond," from L. → trans-, + passer "go by, pass," → pass, → passage.

Tarâraft, tarâraftan, from tarâ-, → trans-, + raft, raftan "to go," → process.

The plane figure formed by three lines intersecting in pairs at three points; a three-sided → polygon. → equilateral triangle, → isosceles triangle, → scalene triangle.

M.E., from O.Fr. triangle, from L. triangulum "triangle," from neuter of adj. triangulus "three-cornered," from tri-, → three, + angulus "corner," → angle.

Seguš "three-cornered," from sé, → three, + guš "corner, → angle."
Sebar "three-sided," from sé, → three, + bar "→ side; breadth; breast."

1) A theorem according to which any side of a triangle is always shorter than the sum of the other two sides.
2) The third requirement for a → distance function describing a → metric space.

→ triangle; → inequality.

In surveying and navigation, the process of deriving the linear distance between any two remote points by the division of a large area into adjacent triangles and using trigonometric relationships. See also → trilateration.

From M.L. triangulation-, from triangulare "to make triangles," → triangle.

Seguš-bandi, from sé, → three, + guš/gušé, → angle, + bandi verbal noun from bastan "to form, bind, tie" (Mid.Pers. bastan/vastan "to bind, shut;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie;" cf. Skt. bandh- "to bind, tie, fasten;" Ger. binden; E. bind; PIE base *bhendh- "to bind").

The Triangle. A small northern constellation between → Andromeda and → Aries, at 2h right ascension, 32° north declination. Its three brightest stars, of magnitudes 3.0, 3.4, and 4.0, form a small, elongated isosceles triangle. One of the constellations listed by Ptolemy. The famous → spiral galaxy → M33 lies in Triangulum. Abbreviation: Tri; genitive: Trianguli.

→ triangle.

The Southern Triangle. A small constellation in the southern hemisphere, at 16h right ascension, 65° south declination, introduced by Johann Bayer (1603). Abbreviation: TrA; genitive: Trianguli Australe

→ traingle; Australe "southern," from auster "south wind," metaphorically extended to "south."

Sebar, → traingle; daštari→ southern.

One of the prominent members of the → Local Group situated in the constellation → Triangulum. Also know as NGC 598. M33 is a type Sc → spiral galaxy seen nearly → face-on. It lies 2.8 million → light-years away and its diameter is 52,000 light-years. M33 is thought to be a satellite of the → Andromeda Galaxy.

→ Triangulum; → galaxy.

The hydrogen molecule composed of three atoms in which one of the atoms is ionized. The molecular ion H₃⁺ plays a key role in the chemistry of gaseous → interstellar medium. It reacts efficiently with almost any neutral atom or molecule to initiate a network of ion-neutral reactions. It is responsible for producing molecules such as OH, CO, and H₂O. The first detection of H₃⁺ in the interstellar medium, via two closely spaced absorption lines (doublet) near 3.668 μm, were reported in two dense → molecular cloud cores along the lines of sight to the embedded → young stellar objects W33A and GL2136 (Geballe & Oka 1996). Since then H₃⁺ has been detected in several molecular clouds. It is believed that H₃⁺ forms via → cosmic ray → ionization of H₂ producing H₂⁺, which quickly reacts to another H₂ molecule to form H₃⁺ ( H₂ + CR → H₂⁺ and H₂⁺ + H₂→ H₃⁺ + H + 1.7 eV).

Tri-, → three; → atomic; → hydrogen; → molecular; → ion.

The property of some crystals of exhibiting three different colors when viewed from three different directions under white lights. → dichroism.

From Gk. tri- "three" + chroic, from chroma "color" + -ism.

Sefâmi, from se, → three, + fâm "color," + -i noun suffix.

A large luminous → H II region in the constellation → Sagittarius. Also known as M20, NGC 6514. Conspicuous → dust lanes radiating from the center appear to divide the nebula in three → lobes. It is a combined → emission nebula and → reflection nebula, extending for nearly 30' on the sky. Its estimated distance is 4100±200 → light-years (Kuhn et al., 2018, arXiv:1807.02115).

Trifid, from L. trifidus "split in three," from → tri- + fidus "divided," from findere "to split;" → nebula.

Miq, → nebula; sepâré "split in three," from sé, → three, + pâré "piece, part, portion, fragment;" Mid.Pers. pârag "piece, part, portion; gift, offering, bribe;" Av. pāra- "debt," from par- "to remunerate, equalize; to condemn;" PIE *per- "to sell, hand over, distribute; to assigne;" cf. L. pars "part, piece, side, share," portio "share, portion;" Gk. peprotai "it has been granted;" Skt. purti- "reward;" Hitt. pars-, parsiya- "to break, crumble."

1a) (n.) Anything, as an act or event, that serves as a stimulus and initiates or precipitates a reaction or series of reactions.
1b) In electronics, the signal or stimulus that initiates a → trigger circuit.
2) (v.) To initiate or precipitate (a chain of events, scientific reaction, psychological process, etc.).

Earlier tricker, from Du. trekker "trigger," from trekken "to pull," from M.Du. trecken (cf. M.L.G. trecken, O.H.G. trechan "to draw").

1) Mâšé "a trigger, tongs, pincers," of unknown origin.
2) Mâšidan, infinitive from mâšé, as above.

A circuit in which a specific predetermined action is initiated by an input pulse.

→ trigger; → circuit

The formation of second-generation stars in a → molecular cloud, as set off by the action of → massive stars. → sequential star formation; → radiation-driven implosion.

→ trigger; → star formation.

Relating to or used in → trigonometry. → trigonometric function.

→ trigonometry; → -ic.