Definition of "Now" :
noun: the momentary present
"Now is a good time to do it."
adverb: in these times
"It is solely by their language that the upper classes nowadays are distinguished."
adverb: without delay or hesitation; with no time intervening
"Come here now!."
adverb: used to preface a command or reproof or request
"Now hear this!."
adverb: at the present moment
"Goods now on sale."
adverb: in the historical present; at this point in the narration of a series of past events
"President Kennedy now calls in the National Guard."
adverb: in the immediate past
"Told me just now."
adverb: (prefatory or transitional) indicates a change of subject or activity
"Now the next problem is...."