now vs while

now

conj
  • Since, because, in light of the fact; often with that. 

adv
  • Used to indicate a context of urgency. 

  • Sometimes; occasionally. 

  • Used to address a switching side, or sharp change in attitude from before. (In this usage, now is usually emphasized). 

  • At the present time. 

  • Used to introduce a point, a qualification of what has previously been said, a remonstration or a rebuke. 

  • At the time reached within a narration. 

  • Differently from the immediate past; differently from a more remote past or a possible future; differently from all other times. 

noun
  • The state of not paying attention to the future or the past. 

  • The present time. 

  • A particular instant in time, as perceived at that instant. 

adj
  • Fashionable; popular; up to date; current. 

  • Present; current. 

intj
  • Indicates a signal to begin. 

while

conj
  • During the same time that. 

  • As long as. 

  • Until. 

  • Used to denote an individual experiencing racial profiling when performing a seemingly benign activity. 

  • Although. 

verb
  • To pass (time) idly. 

  • To occupy or entertain (someone) in order to let time pass. 

noun
  • an uncertain long period of time 

  • an uncertain short moment 

  • An uncertain duration of time, a period of time. 

prep
  • Until. 

How often have the words now and while occurred in a corpus of books? (source: Google Ngram Viewer )