Used other than figuratively or idiomatically: see if, only.
It made me feel better, if only for a moment.
It won't be much fun if only guys turn up to the party.
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.
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!
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.
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!