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

A device for maintaining a system at constant temperature by automatically terminating or restoring the heating or cooling source. It consists of a temperature sensing instrument connected to a switching device. The sensing device is often a bimetallic strip which triggers a simple electric switch.

→ thermo- + → -stat.

1) A controlled and structured list of terms or descriptors usually with a cross-reference system used in subject analysis and information retrieval in a particular field.
2) More generally, a work that lists words arranged and grouped according to their semantic similarities, including synonyms and sometimes antonyms. This is different from the dictionary, which contains definitions and pronunciations. The first major work of this kind in English is Peter Mark Roget's Thesaurus of English words and phrases, Classified and Arranged so as to Facilitate the Expression of Ideas (1852).

From L. thesaurus "treasury, treasure," from Gk.  thesauros  "treasure, treasury, storehouse," from root of  tithenai "to put, to place," → thesis.

Vâžganj, from vâž, → word, + ganj "treasure," from Mid.Pers. ganj "treasure."

1) A proposition put forward for consideration, especially one to be discussed and proved or to be maintained against objections.
Philo.: The first of three stages in Hegelian dialectic; the inevitable transition of thought, by contradiction and reconciliation, from an initial conviction to its opposite and then to a new, higher conception that involves but transcends both of them. → antithesis; → synthesis.
2) A dissertation based on original research, especially as work toward an academic degree.

M.E., from L., from Gk. thesis "a proposition; a setting down, something set down," from root of tithenai "to place, put, set," cognate with Pers. dâdan "to give," as below.

1) Dâyan "giving, setting down," from O.Pers./Av. dā- "to give, grant, put," dadāiti "he gives;" Mid.Pers./Mod.Pers. dâdan "to give; to put" (cf. Skt. dadáti "he gives;" Gk. tithenai "to place, put, set," didomi "I give;" L. dare "to give, offer;" Rus. delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do;" PIE base *dhe- "to put, to do") + -y- epenthetic vowel + -an noun/adjective suffix appearing in many words (such as rowzan, mihan, barzan, rasan, barzan, rowšan).
2) Dâyan-nâme, from dâyan "thesis" + nâme "diploma, letter" (Mid.Pers. nâmag "book, letter, inscription," from O.Pers./Av. nāman- "name;" cf. Skt. nama-; Gk. onoma, onuma; L. nomen; PIE *nomen-).
Pâyân-nâme, literally "ending, final diploma," from pâyân "end," → terminal + nâme.

The proper name of the → extrasolar planet  → Pollux b.

In Greek and Roman mythology, Thestias was the patronym of Leda, → Pollux's mother.

Relatively great in extent from one surface to the opposite; deep or profound. &rarroptically thick

M.E. thikke, O.E. thicce "not thin, dense," from P.Gmc. *theku-, *thekwia- (cf. O.S. thikki, O.H.G. dicchi, Ger. dick), from PIE *tegu- "thick."

Setabr, from Mid.Pers. stabr "strong, big," stambag "pugnacious, opposing;" O.Pers. (mā) stabava [2sg.inj.] "to revolt;" Av. stabra- "strong, firm;" cf. Skt. stabh- "support," stambh- "to support, fix firmly," stabhnāti "supports;" Gk. astemphes "steadfast," stephein "to tie around, encircle," astemphes "firm, rigid;" Lith. stebas "staff, pillar," stembti "to oppose."

A disk component of a → spiral galaxy that lies above the → thin disk and mainly consists of stars. The thick disk of our → Galaxy makes up about 10-50% of the stellar mass of the → Milky Way and has a scale height of ~ 1,000-3,000 → light-years. Thick disk stars are, on average, moving faster in a vertical direction with respect to the → galactic plane than thin disk stars. In contrast to thin disk, the stars within the thick disk are almost all older than 10 billion years and typically have a smaller → metallicity than the average values for the thin disk stars. These facts suggest that the formation scenarios for the thin and thick disks were different. In particular, it is thought that the thick disk is much older than the thin disk.

→ thick; → disk;

A lens whose thickness is not small compared with its focal length. The thick lens may include several components, which may or may not be in contact. → thin lens.

→ thick; → lens.

The state or quality of being thick. → optical thickness.

M.E. thiknesse, O.E. thicnes, from → thick + -nes(s) suffix of action, quality or state, cf. M.Du. -nisse, O.H.G. -nissa, Ger. -nis, Goth. -inassus.

Setabrâ, from setabr→ thick + -â a suffix forming nouns from adjectives.

The part of the human → leg between the → hip and the → knee.

M.E. thi, thigh(e), the(h), O.E. thioh, theoh; cognate with Du. dij, O.H.G. dioh, O.Norse thjo.

Rân, from Mid.Pers. rân "thigh;" Av. rāna- "the outer part of the thigh."

Having relatively little extent from one surface or side to the opposite; not thick. → optically thin; → superthin galaxy.

M.E. thyn(ne), O.E. thynne, from P.Gmc. *thunnuz, *thunw- (cf. W.Fris. ten, M.L.G. dunne, Du. dun, O.H.G. dunni, Ger. dünn), from PIE *tnus-, *tnwi-, from base *ten- "stretch;" cf. Pers. tonok "thin, slender," → attenuate.

Nâzok, from Mid.Pers. nâzuk, nâzik "tender, gentle."

A disk component of a → spiral galaxy containing → stars, → gas, and → dust which are confined to the galaxy's → plane of rotation. In contrast to → thick disks, thin disks contain the bulk of the → baryonic matter in spiral galaxies. For example, on the order of 60-90% of the baryonic matter in the → Milky Way is located in the thin disk. The scale height of the thin disk in the Milky Way is about 400 → light-years, whereas its scale length is about 10,000 light-years. Moreover, the outer regions of thin disks appear to be bent by the → warp phenomenon. The thin disks of spiral galaxies are active sites of → star formation, especially in the spiral arms. For this reason, stars in the thin disk tend to be relatively young. Thin disk stars also tend to be → metal-rich compared with thick disk and → halo stars, and typically have a → metallicity similar to that of the Sun.

→ thin; → disk;

A lens whose thickness is considered small in comparison with the distances generally associated with its optical properties. Such distances are, for example, radii of curvature of the two spherical surfaces, primary and secondary focal lengths, and object and image distances. → thick lens.

→ thin; → lens.

1) A material object without life or consciousness; an inanimate object.
2) Some entity, object, or creature that is not or cannot be specifically designated or precisely described.
3) Anything that is or may become an object of thought (Dictionary.com).

M.E. thing; O.E. þing "meeting, assembly, discussion;" cf. O.Norse þing "assembly, meeting, council;" O.Frisian thing "assembly, action, matter, thing;" O.Saxon thing; O.Du. dinc "law suit, matter, thing;" M.Du. ding; Du. ding; O.Ger. ding, dinc "assembly;" M.H.G. dinc "assembly;" Ger. ding "matter, affairs, thing." Hence, the word originally meant "assembly, meeting," then came to mean a specific issue discussed at such an assembly, and finally came to indicate "an object."

Ciz, from Mid.Pers. ciš, tis "thing, affair;" O.Pers. cišciy "anything."

To employ one's mind rationally and objectively in evaluating or dealing with a given situation.

M.E. thinken, variant of thenken, O.E. thencan; P.Gmc. *thankjan (cf. O.Fris. thinka, O.S. thenkian, O.H.G. denchen, Ger. denken, Goth. thagkjan).

Andišidan, infinitive from andiš-; Mid.Pers. handeš-, handešidan "to think, consider, reflect," ultimately from Proto-Iranian *ham-dis-, from *ham- "together, with, same," → syn- + *dis- "form, appearance," cf. Av. daēs- "to show," daēsa- "sign, omen;" Mod.Pers. dis, disé "form, appearance," variants -diz, -diš; Mid.Pers. dêsag "form, appearance," dêsidan "to form, build;" Sogd. andiš "to seem," andêš "to show," andêšik "appearing;" cf. Skt. deś- "to show, point out;" PIE *deik- "to show" (cf. Gk. deiknumi "to show," dike "manner, custom;" L. dicere "to utter, say;" O.H.G. zeigon, Ger. zeigen "to show;" O.E. teon "to accuse," tæcan "to teach").

Next after the second; the ordinal number for three. → Newton's third law of motion; → third contact; → third dredge-up; → third law of thermodynamics.

M.E. thirde, O.E. (north) thirda, variant of ridda, from P.Gmc. *thridjas (cf. O.Fris. thredda, O.S. thriddio, M.L.G. drudde, Du. derde, O.H.G. dritto, Ger. dritte, Goth. thridja).

Sevom, ordinal number for sé, → three.

The end of the total phase of a solar eclipse marked by the trailing edge of the Moon first revealing the Sun.

→ third; → contact.

A → dredge-up process that occurs in the stellar interior during He shell burning, as in → asymptotic giant branch (AGB) stars. These stars consist of a degenerate carbon-oxygen core, surrounded by a helium-rich region, above which lies a hydrogen-rich convective envelope. Following thermal pulses of the helium-burning shell, the convective envelope moves inward in mass, penetrating the hydrogen-exhausted regions. This is known as third dredge-up. As convection moves inward, nuclear processed materials are carried to the surface.

→ third; → dredge-up.

The → entropy of an idealized state of maximum order is zero at the temperature of → absolute zero. Another version of this law: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.

→ third; → law; → thermodynamics.

The phase of the Moon when half the visible disk of the waning Moon is illuminated. This quarter occurs when the celestial longitude of the Moon is 270° greater than the Sun's.

→ third; → quarter.

A cardinal number, 10 times 3.

M.E. thritty, O.E. thritig, from thri, threo "three" + -tig "group of ten, -ty."

Si, from Mid.Pers. sih; O.Pers. *ciθas nominative singular of *ciθant-; Av. θrisant- "thirty;" cf. Skt. trimśát- "thirty."