Etymology
Advertisement
theater (n.)
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.
Related entries & more 
Advertisement
theatre (n.)
chiefly British English spelling of theater (q.v.); for spelling, see -re.
Related entries & more 
theatrical (adj.)
1550s, "pertaining to the theater;" see theater + -ical. Sense of "stagy, histrionic" is attested from 1709. Related: Theatrically; theatricality.
Related entries & more 
theatrics (n.)
1807, "matters pertaining to the stage," from noun use of theatric (adj.) "pertaining to the theater" (1706), from theater. Meaning "theatrical behavior" is attested from 1929, American English.
Related entries & more 
amphitheater (n.)
late 14c., from Latin amphitheatrum, from Greek amphitheatron "double theater, amphitheater," neuter of amphitheatros "with spectators all around," from amphi "on both sides" (from PIE root *ambhi- "around") + theatron "theater" (see theater). Classical theaters were semi-circles, thus two together made an amphi-theater. They were used by the Romans especially for gladiatorial contests and combats of wild beasts.
Related entries & more 
Advertisement
thaumaturge (n.)

"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, + -ourgia "a working," from ergon "work" (from PIE root *werg- "to do").

Related entries & more 
theory (n.)

1590s, "conception, mental scheme," from Late Latin theoria (Jerome), from Greek theōria "contemplation, speculation; a looking at, viewing; a sight, show, spectacle, things looked at," from theōrein "to consider, speculate, look at," from theōros "spectator," from thea "a view" (see theater) + horan "to see," which is possibly from PIE root *wer- (3) "to perceive."

Earlier in this sense was theorical (n.), late 15c. Sense of "principles or methods of a science or art" (rather than its practice) is first recorded 1610s (as in music theory, which is the science of musical composition, apart from practice or performance). Sense of "an intelligible explanation based on observation and reasoning" is from 1630s.

Related entries & more 
groundling (n.)
"theater patron in the pit" (which originally had no floor or benches), c. 1600, from ground (n.) in an Elizabethan sense of "pit of a theater" + -ling. From the beginning emblematic of bad or unsophisticated taste. Old English grundling was a type of fish.
Related entries & more 
Vic 
1858, colloquial abbreviation of Royal Victoria Theater in London.
Related entries & more 
scenery (n.)
"decoration of a theater stage," 1770, earlier scenary; see scene + -ery. Meaning "a landscape or view, a pictorial scene" is from 1777.
Related entries & more