/if/ , conj.
1. in case that; granting or supposing that; on condition that: Sing if you want to. Stay indoors if it rains. I'll go if you do.
2. even though: an enthusiastic if small audience.
3. whether: He asked if I knew Spanish.
4. (used to introduce an exclamatory phrase): If only Dad could see me now!
5. when or whenever: If it was raining, we had to play inside.
n.
6. a supposition; uncertain possibility: The future is full of ifs.
7. a condition, requirement, or stipulation: There are too many ifs in his agreement.
8. ifs, ands, or buts , reservations, restrictions, or excuses: I want that job finished today, and no ifs, ands, or buts.
[ bef. 900; ME, var. of yif, OE gif, gef; akin to ON ef if, Goth ibai whether, OHG iba condition, stipulation ]
Syn. 1, 2. IF, PROVIDED, PROVIDING imply a condition on which something depends. IF is general. It may be used to indicate suppositions or hypothetical conditions (often involving doubt or uncertainty): If you like, we can go straight home. If I had known, I wouldn't have gone. IF may mean even though: If I am wrong, you are not right. It may mean whenever: If I do not understand, I ask questions. PROVIDED always indicates some stipulation: I will subscribe ten dollars provided ( on the condition ) that you do, too. Provided he goes, we can go along. PROVIDING means the same as PROVIDED, that is, just in case some certain thing should happen: We will buy the house, providing ( provided ) we can get a mortgage.
Usage . IF meaning "whether," as in I haven't decided if I'll go, is sometimes criticized, but the usage has been established in standard English for a long time.
Radio.
See intermediate frequency .
Also, IF .