meantime vs meanwhile

meantime and meanwhile both are nouns.

Word	Noun	Adjective	Verb	Adverb
meantime	Yes	No	No	Yes
meanwhile	Yes	No	No	Yes

As nouns, meantime and meanwhile are synonyms defined as:

meantime and meanwhile: the time between one event, process, or period and another

Other synonyms of meantime include interim, lag.

As adverbs, meantime and meanwhile are synonyms defined as:

Other synonyms of meantime include in the meantime.

meantime (noun)	meanwhile (noun)
the time between one event, process, or period and another	the time between one event, process, or period and another

meantime (adverb)	meanwhile (adverb)
during the intervening time	during the intervening time
	at the same time but in another place