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

Same as → tangential velocity.

→ transverse; → velocity.

A wave in which the vibration or displacement takes place in a plane at right angles to the direction of propagation of the wave; e.g. electromagnetic radiation. → longitudinal wave.

→ transverse; → wave.

The → Zeeman effect when observed at right angles to the orientation of the magnetic field. Un un-displaced line is observed along with a doublet, three lines in all, with the frequencies ν and ν ± Δν. The two displaced components correspond to a plane of → polarization parallel to the external magnetic field and the un-displaced line to a plane of polarization perpendicular to this field. → longitudinal Zeeman effect.

→ transverse; → Zeeman effect.

A four-sided plane figure, no two sides of which are parallel.

L.L. trapezium, from Gk. trapezion "irregular quadrilateral," literally "a little table," diminutive of trapeza "table," from shortening of *tetrapeza, from → tetra- "four" + peza "foot, edge," related to pous, podos, Pers. pâ, → foot.

Zuzanaqé, loan from Ar. dhuzanaqat.

A star cluster located in the center of the → Orion Nebula whose four brightest stars form the vertices of a trapezoid. They are known as θ¹ Ori A, B, C, and D and are of magnitude 6.7, 8.0, 5.1, and 6.7 respectively. They are packed in an area 22 arcseconds across (10,000 A.U.). The Trapezium stars are responsible for the illumination of the entire Orion Nebula. The principal and the most massive star of the group is θ¹Ori C, a young main sequence → O star of type O6. The three others are → B stars. Almost all of the Trapezium stars are multiple: the most massive star θ¹Ori C is double, the next massive star θ¹Ori A is triple, θ¹Ori B is at least quadruple, and θ¹Ori D is apparently single.

→ trapezium; → cluster.

1) The act of traveling, especially to a distant place.
2) To go, move, or journey from one place to another.

M.E. from travailen "to make a journey," originally the same word as Fr. travail "work, labor" (by shift to "make a laborious journey").

Safar, from Ar.

(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.