auditorium (n.) Look up auditorium at Dictionary.com
"part of a public building where people gather to hear speeches, etc.," 1727, from Latin auditorium "a lecture-room," literally "place where something is heard," in Medieval Latin especially "a reception room in a monastery," noun use of neuter of auditorius (adj.) "of or for hearing," from auditus, past participle of audire "to hear" (from PIE root *au- "to perceive"); also see -ory. Earlier in English in the same sense was auditory (late 14c.).