if only vs when

if only

conj
  • Even if for no other reason than; only just. 

  • Used other than figuratively or idiomatically: see if, only. 

  • I wish that; signifies a wish or desire for the present or the future. 

  • I wish that; signifies a regret about an action in the past. 

when

conj
  • Whereas; although; at the same time as; in spite of the fact that. 

  • At (or as soon as) that time that; at the (or any and every) time that; if. 

  • At what time; at which time. 

  • During the time that; at the time of the action of the following clause or participle phrase. 

  • Since; given the fact that; considering that. 

pron
  • What time; which time. 

intj
  • That's enough: a command asking someone to stop adding something, especially an ingredient or portion of food or drink; used in, or as if in, literal response to 'Say when'. 

noun
  • The time at which something happens. 

adv
  • At which, on which, during which: often omitted or replaced with that. 

  • A circumstance or situation in which. 

  • The time at, on or during which. 

  • At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time. 

  • At an earlier time and under different, usually less favorable, circumstances. 

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