If \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 [OE]dipus 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.

Source: Webster's Revised Unabridged Dictionary (1913)