word-forming element active from mid-19c. and meaning "art, craft, skill," later "technical, technology," from Latinized form of Greek tekhno-, combining form of tekhnē "art, skill, craftsmanship, craft in work; method, system, an art, a system or method of making or doing," from PIE *teks-na- "craft" (of weaving or fabricating), from suffixed (or reduplicated) form of root *teks- "to weave," also "to fabricate."

before vowels properly tel-, word-forming element of Greek origin meaning "far, far off, operating over distance," from Greek tēle "far off, afar, at or to a distance," related to teleos (genitive telos) "end, goal, completion, result" (from PIE root *kwel- (2) "far" in space or time).

The element also could mean "telegraph" by mid-19c. (teleprinter); "telephone" by late 19c. (telecopier), "television" by 1928 (tele-talkie, "motion picture broadcast by television"); and "by electronic means" by 1981 (teleshopping, originally hypothetical).

word-forming element meaning "thrice, three times," from Latin ter "thrice," from *tris-, from root of three. Compare Latin tertius "third."

word-forming element of Greek origin used from mid-20c. in forming large units of measure and meaning "trillion," adopted by 1947 as tira-, 1951 as tera-, from Greek teras "marvel, monster" (see terato-). As in terabyte.

before vowels tetr-, word-forming element of Greek origin meaning "four," from Greek tetra-, combining form of tettares (Attic), tessares "the numeral four," equivalent to Latin quattor, from PIE root *kwetwer- "four." The equivalent of Latin quadri-.

before vowels thalass-, word-forming element of Greek origin meaning "sea, the sea," from Greek thalassa "the sea" (in Homer, when used of a particular sea, "the Mediterranean," as opposed to ōkeanos), a word from the Pre-Greek substrate language. In Attic Greek thalatta, hence sometimes thalatto-.

before vowels thanat-, word-forming element of Greek origin used in English from 19c., mostly in scientific words, and 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."

before vowels thec-, word-forming element of Greek origin used since 19c. in botany and zoology with a sense of "case, capsule;" from Latinized combining form of Greek thēkē "case, receptacle" (from suffixed form of PIE root *dhe- "to set, put"). Sometimes theci-, in Latinized form.

word-forming element of Greek origin meaning "god, gods, God," from Greek theos "god," which is reconstructed to be from PIE root *dhes-, forming words for religious concepts, such as Latin feriae "holidays," festus "festive," fanum "temple."

often thero-, word-forming element meaning "beast," from Greek thēr "wild beast, beast of prey" (from PIE root *ghwer- "wild beast"). Also therio-, theri-, from Greek thērion "wild animal, hunted animal," diminutive of thēr.