If  —conj. 1 introducing a conditional clause: a on the condition or supposition that; in the event that (if he comes i will tell him; if you are tired we can rest). B (with past tense) implying that the condition is not fulfilled (if i knew i would say). 2 even though (i'll finish it, if it takes me all day). 3 whenever (if i am not sure i ask). 4 whether (see if you can find it). 5 expressing a wish, surprise, or request (if i could just try!; if it isn't my old hat!; if you wouldn't mind?). —n. Condition, supposition (too many ifs about it).  if only 1 even if for no other reason than (i'll come if only to see her). 2 (often ellipt.) Expression of regret; i wish that (if only i had thought of it). [old english]