now vs nowadays

now and nowadays both are nouns.

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

As nouns, nowadays is a hypernym of now; that is, nowadays is a word with a broader meaning than now:

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

Other hypernyms of now include present.

As adverbs, now and nowadays are synonyms defined as:

Other synonyms of now include today.

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

now (adverb)	nowadays (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