nowadays vs now

nowadays and now both are nouns.

Word	Noun	Adjective	Verb	Adverb
nowadays	Yes	No	No	Yes
now	Yes	No	No	Yes

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

nowadays: the period of time that is happening now; any continuous stretch of time including the moment of speech
now: the momentary present

Other hyponyms of nowadays include here and now, moment, present moment, date, nonce, time being, today, tonight.

As adverbs, nowadays and now are synonyms defined as:

Other synonyms of nowadays include today.

nowadays (noun)	now (noun)
the period of time that is happening now; any continuous stretch of time including the moment of speech	the momentary present

nowadays (adverb)	now (adverb)
in these times	in these times
	without delay or hesitation; with no time intervening
	used to preface a command or reproof or request
	at the present moment
	in the historical present; at this point in the narration of a series of past events
	in the immediate past
	(prefatory or transitional) indicates a change of subject or activity