if vs now

if

conj
  • Supposing that; given that; supposing it is the case that. 

  • Although; used to introduce a concession. 

  • Supposing that; used with past or past perfect subjunctive indicating that the condition is closed. 

  • Supposing that, assuming that, in the circumstances that; used to introduce a condition or choice. 

  • Whether; used to introduce a noun clause, an indirect question, that functions as the direct object of certain verbs. 

  • Even if; even in the circumstances that. 

  • In the event that a statement is true (a programming statement that acts in a similar manner). 

  • Introducing a relevance conditional. 

noun
  • An uncertainty, possibility, condition, doubt etc. 

now

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

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. 

intj
  • Indicates a signal to begin. 

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. 

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

  • Present; current. 

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