if only

conjunction4

1. •
   I wish that; would (that) (archaic). Signifies a wish or desire for the present or the future.

   • If only I could win the lottery.
   • My gambling ex could come to his senses, if only.
2. •
   I wish that; would (that) (archaic). Signifies a regret about an action in the past.

   • If only I had listened to my parents.
   • We didn't have that luxury. If only!
3. •
   Even if for no other reason than; only just.

   • I was pretty sure what I wanted, but I still tried on another if only to make sure.
4. •
   Signifies a hypothetical or wishful precondition, or one which would be simple but is nonetheless unlikely, for a hypothetical, counterfactual, or future outcome.

   • He could be a great student if only he got [or: if he only got] a little non-judgmental encouragement.
   • If you'd only quit interrupting me, I'll tell you!