repeat vs replay

repeat and replay both are nouns.

Word	Noun	Adjective	Verb	Adverb
repeat	Yes	No	Yes	No
replay	Yes	No	Yes	No

As nouns, replay is a hyponym of repeat; that is, replay is a word with a more specific, narrower meaning than repeat:

Other hyponyms of repeat include sequence, cycle, rematch, recurrence, return.

repeat (noun)	replay (noun)
an event that repeats	the immediate rebroadcast of some action (especially sports action) that has been recorded on videotape
	something (especially a game) that is played again

repeat (verb)	replay (verb)
happen or occur again	play again
to say, state, or perform again	repeat a game against the same opponent
to say again or imitate	play (a melody) again
make or do or perform again	reproduce (a recording) on a recorder
repeat an earlier theme of a composition
do over