textbook (n.) Look up textbook at Dictionary.com
also text-book, "book used by students," 1779, from text (n.) + book (n.). Earlier (1730) it meant "book printed with wide spaces between the lines" for notes or translation (such a book would have been used by students), from the notion of the text of a book being more open than the close notes. As an adjective from 1916.
textile (n.) Look up textile at Dictionary.com
1620s, from Latin textilis "a web, canvas, woven fabric, cloth, something woven," noun use of textilis "woven, wrought," from texere "to weave," from PIE root *teks- "to weave," also "to fabricate." As an adjective from 1650s.
textual (adj.) Look up textual at Dictionary.com
late 14c., textuel "of or pertaining to text," also "well-read," from Old French textuel, from Latin textus (see text). English spelling conformed to Latin from late 15c. Related: Textually.
texture (n.) Look up texture at Dictionary.com
early 15c., "network, structure," from Middle French texture and directly from Latin textura "web, texture, structure," from stem of texere "to weave," from PIE root *teks- "to weave, to fabricate, to make; make wicker or wattle framework" (source also of Sanskrit taksati "he fashions, constructs," taksan "carpenter;" Avestan taša "ax, hatchet," thwaxš- "be busy;" Old Persian taxš- "be active;" Latin tela "web, net, warp of a fabric;" Greek tekton "carpenter," tekhne "art;" Old Church Slavonic tesla "ax, hatchet;" Lithuanian tasau "to carve;" Old Irish tal "cooper's ax;" Old High German dahs, German Dachs "badger," literally "builder;" Hittite taksh- "to join, unite, build"). Meaning "structural character" is recorded from 1650s. Related: Textural.
texture (v.) Look up texture at Dictionary.com
1888 (implied in textured), "to give a texture to, to make not smooth or plain," from texture (n.).
TGIF Look up TGIF at Dictionary.com
also T.G.I.F., by 1946, slang abbreviation of "Thank God (or "goodness"), it's Friday" (end of the work week).
th Look up th at Dictionary.com
A sound found chiefly in words of Old English, Old Norse or Greek origin, unpronounceable by Normans and many other Europeans. In Greek, the sound corresponds etymologically to Sanskrit -dh- and English -d-; and it was represented graphically by -TH- and at first pronounced as a true aspirate (as still in English outhouse, shithead, etc.). But by 2c. B.C.E. the Greek letter theta was in universal use and had the modern "-th-" sound. Latin had neither the letter nor the sound, however, and the Romans represented Greek theta by -TH-, which they generally pronounced, at least in Late Latin, as simple "-t-" (passed down to Romanic languages, as in Spanish termal "thermal," teoria "theory," teatro "theater").

In Germanic languages it represents PIE *-t- and was common at the start of words or after stressed vowels. To represent it, Old English and Old Norse used the characters ð "eth" (a modified form of -d-) and þ "thorn," which originally was a rune. Old English, unlike Old Norse, seems never to have standardized which of the two versions of the sound ("hard" and "soft") was represented by which of the two letters.

The digraph -th- sometimes appears in early Old English, on the Roman model, and it returned in Middle English with the French scribes, driving out eth by c. 1250, but thorn persisted, especially in demonstratives (þat, þe, þis, etc.), even as other words were being spelled with -th-. The advent of printing dealt its death-blow, however, as types were imported from continental founders, who had no thorn. For a time y was used in its place (especially in Scotland), because it had a similar shape, hence ye for the in historical tourist trap Ye Olde _______ Shoppe (it never was pronounced "ye," only spelled that way).

The awareness that some Latin words in t- were from Greek th- encouraged over-correction in English and created unetymological forms such as Thames and author, while some words borrowed from Romanic languages preserve, on the Roman model, the Greek -th- spelling but the simple Latin "t" pronunciation (as in Thomas and thyme).
Thaddeus Look up Thaddeus at Dictionary.com
masc. proper name, from Latin Thaddaeus, from Greek Thaddaios, from Talmudic Hebrew Tadday. Klein derives this from Aramaic tedhayya (pl.) "breasts." Thayer's "Greek-English Lexicon of the New Testament" suggests the sense might be "large-hearted," hence "courageous." In the Bible, a surname of the apostle Jude, brother of James the Less.
Thai Look up Thai at Dictionary.com
1808, native name, Tai, literally "free."
Thailand Look up Thailand at Dictionary.com
from Thai, indigenous name of the inhabitants, + land (n.). Also see Siam.
thalamus (n.) Look up thalamus at Dictionary.com
plural thalami, 1753, "the receptacle of a flower," Modern Latin, from Latin thalamus "inner chamber, sleeping room" (hence, figuratively, "marriage, wedlock"), from Greek thalamos "inner chamber, bedroom," related to thalame "den, lair," tholos "vault, vaulted building." Used in English since 1756 of a part of the forebrain where a nerve appears to originate.
thalassemia (n.) Look up thalassemia at Dictionary.com
from thalasso- "sea" + haima "blood" (see -emia).
thalasso- Look up thalasso- at Dictionary.com
before vowels thalass-, word-forming element meaning "sea, the sea," from Greek thalassa "the sea" (in Homer, when used of a particular sea, "the Mediterranean," as opposed to okeanos), a word from a lost pre-Greek Mediterranean language. In Attic Greek thalatta, hence sometimes thalatto-.
thaler (n.) Look up thaler at Dictionary.com
old German silver coin; see dollar.
Thalia Look up Thalia at Dictionary.com
fem. proper name, from Latinized form of Greek Thaleia, "the joyful Muse," presiding over comedy and idyllic poetry, literally "the blooming one," fem. proper name from adjective meaning "blooming, luxuriant, bounteous," from thallein "to bloom," related to thalia "abundance," thallos "young shoot" (see thallus). Also the name of one of the three Graces, patroness of festive meetings.
Thalidomide (n.) Look up Thalidomide at Dictionary.com
1958, from "phthalimidoglutarimide," based on abbreviated form of naphthalene; a morning-sickness drug responsible for severe birth defects in Europe from 1956 to 1961, when it was withdrawn. It never was approved for use in America thanks to the efforts of Dr. Helen Brooke Taussig (1898-1986). Thalidomide baby is attested from 1962.
thallium (n.) Look up thallium at Dictionary.com
rare metallic element, 1861, Modern Latin, from Greek thallos "young shoot, green branch" (see thallus) + element name ending -ium. So called by its discoverer, Sir William Crookes (1832-1919), from the green line in its spectrum by which he detected it. Related: Thallic.
thallus (n.) Look up thallus at Dictionary.com
1829, Latin, from Greek thallos "green shoot, young branch, twig," related to thalia "abundance," thalos "scion, child," ultimately from PIE root *dhal- "to bloom" (source also of Armenian dalar "green, fresh," Albanian dal' "I sprout," Old Irish duilesc, a type of algae).
thalweg (n.) Look up thalweg at Dictionary.com
1831, from German Thalweg "path along the bottom of a valley," from thal (see dale) + weg "road, path" (see way (n.)).
Thames Look up Thames at Dictionary.com
river through London, Old English Temese, from Latin Tamesis (51 B.C.E.), from British Tamesa, an ancient Celtic river name perhaps meaning "the dark one." The -h- is unetymological (see th).
Thammuz (n.) Look up Thammuz at Dictionary.com
1530s, from Hebrew tammuz, tenth month of the Jewish civil year, fourth of the sacred, covering parts of June and July; also the name of a Syrian deity equivalent to Phoenician Adon, whose festival began with the new moon of this month (compare Tammuz).
than (conj.) Look up than at Dictionary.com
Old English þan, conjunctive particle used after a comparative adjective or adverb, from þanne, þænne, þonne "then" (see then). Developed from the adverb then, and not distinguished from it by spelling until c. 1700.

The earliest use is in West Germanic comparative forms introducing the second member, i.e. bigger than (compare Dutch dan, German denn), which suggests a semantic development from the demonstrative sense of then: A is bigger than B, evolving from A is bigger, then ("after that") B. Or the word may trace to Old English þonne "when, when as," such as "When as" B is big, A is more (so).
thanage (n.) Look up thanage at Dictionary.com
c. 1400, from Anglo-French thaynage (c. 1300), from English thane + Old French suffix -age (see -age).
thanatism (n.) Look up thanatism at Dictionary.com
belief that at death the soul ceases to exist, 1900, from thanato- + -ism.
thanato- Look up thanato- at Dictionary.com
before vowels thanat-, word-forming element meaning "death," from Greek thanatos "death," from PIE *dhwene- "to disappear, die," perhaps from a root meaning "dark, cloudy" (compare Sanskrit dhvantah "dark"). Hence Bryant's "Thanatopsis", with Greek opsis "a sight, view."
thanatology (n.) Look up thanatology at Dictionary.com
"scientific study of death," 1837, from thanato- "death" + -logy. In 1970s, some undertakers made a bid to be called thanatologists; but from 1974 that word has been used principally in reference to specialists in the needs of the terminally ill.
thanatos (n.) Look up thanatos at Dictionary.com
"death instinct," 1935, in Freudian psychology, from Greek thanatos "death" (see thanato-).
thane (n.) Look up thane at Dictionary.com
Old English þegn "military follower, one who holds lands in exchange for military service," also "vassal, retainer, attendant," from Proto-Germanic *thegnas (source also of Old Saxon thegan "follower, warrior, boy," Old Norse þegn "thane, freeman," Old High German thegan, German Degen "thane, warrior, hero"), from PIE *tek-no- (source also of Sanskrit takman "descendant, child," Greek teknon "child"), from root *tek- "to beget, give birth to" (source also of Greek tekos "child, the young of animals," tokos "childbirth, offspring, produce of money, interest"). Also used in Old English for "disciple of Christ." Specific sense of "man who ranks between an earl and a freeman" is late 15c.

The modern spelling is from Scottish, where early 13c. it came to mean "chief of a clan, king's baron," and it has predominated in English probably due to the influence of "Macbeth;" normal orthographic changes from Old English ðegn would have produced Modern English *thain. Some historians now use thegn to distinguish Anglo-Saxon thanes from Scottish thanes.
thang (n.) Look up thang at Dictionary.com
by 1937, representing in print a Southern U.S. pronunciation thing.
thank (v.) Look up thank at Dictionary.com
Old English þancian, þoncian "to give thanks, thank, to recompense, to reward," from Proto-Germanic *thankojan (source also of Old Saxon thancon, Old Norse þakka, Danish takke, Old Frisian thankia, Old High German danchon, Middle Dutch, Dutch, German danken "to thank"), from *thankoz "thought; gratitude," from PIE root *tong- "to think, feel."

It is related phonetically to think as song is to sing; for sense evolution, compare Old High German minna "loving memory," originally "memory." Also compare related Old English noun þanc, þonc, originally "thought," but also "good thoughts, gratitude." In ironical use, "to blame," from 1550s. To thank (someone) for nothing is recorded from 1703. Related: Thanked; thanking.
thank you Look up thank you at Dictionary.com
polite formula used in acknowledging a favor, c. 1400, short for I thank you (see thank). As a noun, from 1792.
thankful (adj.) Look up thankful at Dictionary.com
Old English þancful "satisfied, grateful," also "thoughtful, ingenious, clever;" see thank + -ful. Related: Thankfully; thankfulness. Thankfully in the sense "thankful to say" is attested by 1966, but deplored by purists (compare hopefully).
thankless (adj.) Look up thankless at Dictionary.com
"likely to not be rewarded with thanks," 1540s, from thank + -less. Related: Thanklessly; thanklessness.
thanks (n.) Look up thanks at Dictionary.com
mid-13c., plural of thank (n.), from Old English þanc, þonc in its secondary sense "grateful thought, gratitude," from the same root as thank (v.). In prehistoric times the Germanic noun seems to have expanded from "a thinking of, a remembering" to also mean "remember fondly, think of with gratitude." Compare Old Saxon thank, Old Frisian thank, Old Norse þökk, Dutch dank, German Dank. The Old English noun chiefly meant "thought, reflection, sentiment; mind, will, purpose," also "grace, mercy, pardon; pleasure, satisfaction."

As short for I give you thanks from 1580s; often with extensions, such as thanks a lot (1908). Spelling thanx attested by 1907.
thanksgiving (n.) Look up thanksgiving at Dictionary.com
1530s, "the giving of thanks," from thanks (n.) + present participle of give (v.). In the specific sense of "public celebration acknowledging divine favors" thanksgiving dates from 1630s (the first one in America was held October 1621 by Plymouth Colony Pilgrims in appreciation of assistance from members of the Massasoit tribe and celebration of the first harvest); though Thanksgiving Day itself is not attested until 1670s.
thar Look up thar at Dictionary.com
now representing dialectal pronunciation of there; in literary use in Middle English.
that (pron.) Look up that at Dictionary.com
Old English þæt, "that, so that, after that," neuter singular demonstrative pronoun ("A Man's a Man for a' that"), relative pronoun ("O thou that hearest prayer"), and demonstrative adjective ("Look at that caveman go!"), corresponding to masc. se, fem. seo. From Proto-Germanic *that, from PIE *tod-, extended form of demonstrative pronominal base *-to- (see -th (1)). With the breakdown of the grammatical gender system, it came to be used in Middle English and Modern English for all genders. Germanic cognates include Old Saxon that, Old Frisian thet, Middle Dutch, Dutch dat "that," German der, die, das "the."

Generally more specific or emphatic than the, but in some cases they are interchangeable. From c. 1200 opposed to this as indicating something farther off. In adverbial use ("I'm that old"), in reference to something implied or previously said, c. 1200, an abbreviation of the notion of "to that extent," "to that degree." Slang that way "in love" first recorded 1929. That-a-way "in that direction" is recorded from 1839. "Take that!" said while delivering a blow, is recorded from early 15c.
thatch (v.) Look up thatch at Dictionary.com
late 14c., thecchen, from Old English þeccan "to cover, cover over, conceal," in late Old English specifically "cover the roof of a house," related to þæc "roof, thatching material," from Proto-Germanic *thakjan (source also of Old Saxon thekkian, Old Norse þekja, Old Frisian thekka, Middle Dutch decken, Dutch dekken, Old High German decchen, German decken "to cover"), from PIE root *(s)teg- "to cover."
thatch (n.) Look up thatch at Dictionary.com
Old English þæc "roof, thatch, cover of a building," from Proto-Germanic *thakam (source also of Old Norse þak, Old Frisian thek, Swedish tak, Danish tag, Middle Dutch, Dutch dak "roof," Old High German dah "covering, cover," German Dach "roof"), from PIE root *(s)teg- "to cover."
thatcher (n.) Look up thatcher at Dictionary.com
early 14c. (late 12c. as a surname); agent noun from thatch (v.). Corresponds to Old English þecere, Dutch dekker, German Decker. Thatcherite in British politics (1976) refers to policies and principles of Conservative politician and prime minister Margaret Thatcher (1925-2013).
thaught (n.) Look up thaught at Dictionary.com
"rower's bench," 1620s, alteration of thoft, from Old English þofte, from Proto-Germanic *thufto- (source also of Dutch doft, German ducht), from PIE *tupta-, from root *tup- "to squat."
thaumaturge (n.) Look up thaumaturge at Dictionary.com
"wonder-worker," 1715, from Medieval Latin thaumaturgus, from Greek thaumatourgos "wonder-working; conjurer," from thauma (genitive thaumatos) "wonder, astonishment; wondrous thing," literally "a thing to look at," from root of theater, + ergon "work" (from PIE root *werg- "to do").
thaumaturgy (n.) Look up thaumaturgy at Dictionary.com
"wonder-working," 1727, from Greek thaumatourgia, from thaumatourgos (see thaumaturge). Related: Thaumaturgic; thaumaturgical (1620s).
thaw (v.) Look up thaw at Dictionary.com
Old English þawian (transitive), from Proto-Germanic *thawon- (source also of Old Norse þeyja, Middle Low German doien, Dutch dooien, Old High German douwen, German tauen "to thaw"), from PIE root *ta- "to melt, dissolve" (source also of Sanskrit toyam "water," Ossetic thayun "to thaw," Welsh tawadd "molten," Doric Greek takein "to melt, waste, be consumed," Old Irish tam "pestilence," Latin tabes "a melting, wasting away, putrefaction," Old Church Slavonic tajati "to melt"). Intransitive sense from early 14c. Related: Thawed; thawing.
thaw (n.) Look up thaw at Dictionary.com
"the melting of ice or snow," also "spell of weather causing this," c. 1400, from thaw (v.). Figurative sense is from 1590s; specifically "relaxation of political harshness or hostility" from 1950, an image from the "Cold War."
THC (n.) Look up THC at Dictionary.com
active ingredient in marijuana and hashish, 1968, short for tetrahydrocannabinol (1940).
the Look up the at Dictionary.com
definite article, late Old English þe, nominative masculine form of the demonstrative pronoun and adjective. After c.950, it replaced earlier se (masc.), seo (fem.), þæt (neuter), and probably represents se altered by the th- form which was used in all the masculine oblique cases (see below).

Masc. Fem. Neut. Plural
Nom. se seo þæt þa
Acc. þone þa þæt þa
Gen. þæs þære þæs þara
Dat. þæm þære þæm þæm
Inst. þy, þon -- þy, þon --

Old English se is from PIE root *so- "this, that" (source also of Sanskrit sa, Avestan ha, Greek ho, he "the," Irish and Gaelic so "this"). For the þ- forms, see that. The s- forms were entirely superseded in English by mid-13c., excepting a slightly longer dialectal survival in Kent. Old English used 10 different words for "the" (see table), but did not distinguish "the" from "that." That survived for a time as a definite article before vowels (that one or that other).

Adverbial use in the more the merrier, the sooner the better, etc. is a relic of Old English þy, the instrumentive case of the neuter demonstrative (see that).
Thea Look up Thea at Dictionary.com
fem. proper name, from Greek thea "goddess," fem. equivalent of theos "god" (from PIE root *dhes-, forming words for religious concepts).
theater (n.) Look up theater at Dictionary.com
late 14c., "open air place in ancient times for viewing spectacles and plays," from Old French theatre (12c., Modern French théâtre, improperly accented) and directly from Latin theatrum "play-house, theater; stage; spectators in a theater" (source also of Spanish, Italian teatro), from Greek theatron "theater; the people in the theater; a show, a spectacle," literally "place for viewing," from theasthai "to behold" (related to thea "a view, a seeing; a seat in the theater," theates "spectator") + -tron, suffix denoting place.

Meaning "building where plays are shown" is from 1570s in English. Transferred sense of "plays, writing, production, the stage" is from 1660s. Generic sense of "place of action" is from 1580s; especially "region where war is being fought" (1914). Spelling with -re arose late 17c. and prevailed in Britain after c. 1700 by French influence, but American English retained or revived the older spelling in -er.
theatre (n.) Look up theatre at Dictionary.com
chiefly British English spelling of theater (q.v.); for spelling, see -re.