Words related to theater

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.
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").

theatre (n.)
chiefly British English spelling of theater (q.v.); for spelling, see -re.
theatrical (adj.)
1550s, "pertaining to the theater;" see theater + -ical. Sense of "stagy, histrionic" is attested from 1709. Related: Theatrically; theatricality.
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.
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.