operating theatre vs operating room

operating theatre and operating room both are nouns.

Word	Noun	Adjective	Verb	Adverb
operating theatre	Yes	No	No	No
operating room	Yes	No	No	No

As nouns, operating theatre and operating room are synonyms defined as:

operating theatre and operating room: a room in a hospital equipped for the performance of surgical operations

Other synonyms of operating theatre include operating theater, OR, surgery.

operating theatre (noun)	operating room (noun)
a room in a hospital equipped for the performance of surgical operations	a room in a hospital equipped for the performance of surgical operations