“if” – English explanatory dictionary

conj 1. showing what might happen ○ If he’s going to be late, he should send me a text to warn me. ○ If it freezes tonight, the paths will be slippery tomorrow. ○ If I’m in London, I’ll come and see you. ○ If he had told me you were ill, I’d have come to see you in hospital. ○ If I won the lottery, I would take a long holiday. 2. asking questions ○ Do you know if the plane is late? ○ I was wondering if you would like to have some tea. 3. although ○ He is nice, if rather lazy. ■ noun a question which is not certain ○ He’ll catch the plane if he gets up in time – and that’s a very big if.!

conj. [OE. if, gif, AS. gif; akin to OFries. ief, gef, ef, OS. ef, of, D. of, or, whether, if, G. ob whether, if, OHG. oba, ibu, Icel. ef, Goth. iba, ibai, an interrogative particle; properly a case form of a noun meaning, doubt (cf. OHG. iba doubt, condition, Icel. if, ef, ifi, efi), and therefore orig. meaning, on condition that.]
1. In case that; granting, allowing, or supposing that; — introducing a condition or supposition. “Tisiphone, that oft hast heard my prayer,
Assist, if Œdipus deserve thy care.” Pope. “If thou be the Son of God, command that these stones be made bread.” Matt. iv. 3.
2. Whether; — in dependent questions. “Uncertain if by augury or chance.” Dryden. “She doubts if two and two make four.” Prior. As if, But if. See under As, But.