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

The second innermost satellite of → Neptune. It was discovered using NASA's Voyager 2 mission in 1989. It orbits 50,070 km from the center of Neptune and is about 80 km in diameter.

Named after a daughter of Aether and Hemera from Gk. mythology. Thalassa is also the Greek word for "sea".

The fourth-closest of → Jupiter's known → satellites, also known as Jupiter XIV. Thebe is 100 x 90 km in diameter and orbits its planet at 222,000 km in 0.6745 (Earth) day. It is in synchronous rotation, i.e. always keeps the same side facing Jupiter. Thebe was discovered by Stephen Synnott (Voyager 1) in 1979.

In Gk. mythology, Thebe was a nymph, daughter of the river god Asopus.

A hypothetical → protoplanet that collided with → earth some 4.5 billion years ago. Debris from the collision, a mixture of material from both bodies, spun out into Earth orbit and → coalesced into the → Moon. This scenario explains many aspects of → lunar geology including the size of the Moon's → core and the → density and → isotopic  → composition of Moon rocks.

Named for Theia, the mythical Greek Titan who was the mother of Selene, the goddess of the Moon.

The belief in one God as the creator and ruler of the universe, without rejection of revelation (distinguished from → deism).
2) Belief in the existence of a god or gods (opposed to → atheism) (Dictionary.com).

From the- variant of theo- before a vowel, from Gk. theos "god," from PIE root *dhes-, root of words applied to various religious concepts, such as L. feriae "holidays," festus "festive," fanum "temple."

Yzadân-bâvari, from yazdân "god," from Mid.Pers. yazetân "gods," ultimately from Proto-Ir. *iaz- "to sacrifice, worship, venerate," → deity.

A person who believes in → theism.

→ theism; → -ist

Of or relating to a → theme.

→ thematics.

A body of topics for study or discussion.

From L. themat-, from thema, → theme, + → -ics.

The act or process of thematizing.

→ thematize; → -tion.

Present or select as a theme.

From L. themat-, from thema, → theme, + E. suffix → -ize.

Verbal noun of nedanidan, → thematize.

1) Generally, a topic or subject of discourse, discussion, meditation, or composition.
2) A unifying or dominant idea, motif, etc., as in a work of art. More specifically, an implicit central concept or message found in a literary work.
3) A recurrent melodic element in a musical composition.
4) Linguistics: The stem of a noun or verb; the part to which inflections are added, especially one composed of the root and an added vowel.

M.E. teme, theme, from O.Fr. tesme, from L. thema "a subject, thesis," from Gk. thema "a proposition, subject, deposit," literally "something set down," from PIE root *dhe- "to set, put."

Nedan, literally "(something) set down," from prefix ne- "down," → ni- (PIE), + da-, variant of dâ-/dâdan "to give, set" (dah-/dahad "gives"); Mid.Pers. dâdan, dah- "to give, set; create;" O.Pers. dā- "to give;" Av. dā- "to place upon, bestow;" Proto-Ir. *da- "to give" (cf. Skt. dā- "to give, present, offer;" Gk. thema; PIE *dhe- "to set, put," as above) + word forming suffix -an (as in rowzan, rasan, anjoman, barzan).

A small satellite of → Jupiter, ninth in order from the planet. It is about 8 km in diameter and orbits Jupiter at a mean distance of 7 500 000 km every 130 days. It was discovered in 1975, lost, and then rediscovered in 2000. Also known as Jupiter XVIII.

Named after Themisto, daughter of the river god Inachus, who became the mother of Ister (the river Danube) by Zeus (Jupiter).

1) A form of government in which → God or a → deity is recognized as the supreme civil ruler, the God's or deity's laws being interpreted by the ecclesiastical authorities.
2) A system of government by priests claiming a divine commission (Dictionary.com)

→ theism; → -cracy.

An instrument for the measurement of angles, used in surveying. It consists essentially of a telescope moving along a circular scale graduated in degrees.

The first occurrence of the word theodolite is found in the surveying textbook A geometric practice named Pantometria (1571) by Leonard Digges, which was published posthumously by his son, Thomas Digges. The etymology of the word is unknown. The first part of the New Latin theo-delitus might stem from the Gk. theaomai "to behold, view attentively, contemplate," but the second part is more puzzling and is often attributed to an un-scholarly variation of delos "evident, clear."

A person versed in theology, especially Christian theology (Dictionary.com)

→ theology.

The field of study and analysis that treats of → God and of God's attributes and relations to the universe; study of divine things or religious truth; divinity (Dictionary.com).

→ theism; → -logy.

A → proposition, → statement, or → formula in → mathematics or → logic deduced from → axioms, other propositions, → assumptions, → premises, or formulas. Theorems are statements which can be proved. For example, → Fourier theorem; → Liouville's theorem; → Woltjer's theorem.

From M.Fr. théorème, from L.L. theorema, from Gk. theorema "spectacle, speculation," in Euclid "proposition to be proved," from theorein "to look at, speculate, consider."

Farbin, from far- intensive prefix "much, abundant; elegantly; forward" (Mid.Pers. fra- "forward, before; much; around;" O.Pers. fra- "forward, forth;" Av. frā, fərā-, fra- "forward, forth; excessive;" cf. Skt. prá- "before; forward, in front;" Gk. pro "before, in front of;" L. pro "on behalf of, in place of, before, for;" PIE *pro-) + bin, present stem of didan "to see," from Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" cf. Skt. veda "I know;" Gk. oida "I know," idein "to see;" L. videre "to see;" PIE base *weid- "to know, to see."

Of, pertaining to, or consisting in theory.

From L.L. theoreticus "of or pertaining to theory," from Gk. theoretikos "contemplative, pertaining to theory;" → theory.

Negarik, contraction of negaréik, from negaré→ theory + -ik, → -ic.

An astrophysical study or research group mainly concerned with theory rather than observation.

→ theoretical; → astrophysics.

One who formulates or is expert in the theoretical side of a subject.

From theoretic, from theoretics, from → theory + -ian.

Negare-pardâz, from negaré, → theory, + pardâz, present stem of pardâxtan "to accomplish; bring to perfection; to attempt, to care; to clean; to free;" Mid.Pers. pardâxtan, pardâzidan "to accomplish; to be done with, freed of" ultimately from Proto-Iranian *para-tāxta-, *para-tāca- "to take away; to expel," from *para- "along, forth," → para-, + tāxta-, tāca- "to run, to flow;" cf. Av. tak- "to run, to flow;" Mod.Pers. tâxtan, tâz- "to flow, to cause to walk," → flow.

Same as → theoretician.

From theor-, from → theory + -ist a suffix of nouns, often corresponding to verbs ending in -ize or nouns ending in -ism.

→ theoretician.