Etimology
From Middle English if, yif, yef, from Old English ġif (“if”), from Proto-West Germanic *jabu, *jabē, from Proto-Germanic *jabai (“when, if”). Cognate with Scots gif (“if, whether”), Saterland Frisian af, of (“if, whether”), West Frisian oft (“whether”), Dutch of (“or, whether, but”), Middle Low German ef, if, af, of ("if; whether"; > German Low German of), German ob (“if, whether”), Icelandic ef (“if”).
conjunction
if
Supposing that, assuming that, in the circumstances that; used to introduce a condition or choice.
(computing) In the event that a statement is true (a programming statement that acts in a similar manner).
Supposing that; used with past or past perfect subjunctive indicating that the condition is closed.
Supposing that; given that; supposing it is the case that.
Although; used to introduce a concession.
(sometimes proscribed) Whether; used to introduce a noun clause, an indirect question, that functions as the direct object of certain verbs.
(usually hyperbolic) Even if; even in the circumstances that.
Introducing a relevance conditional.
Examples
If it rains, I shall get wet.
I'll do it next year —if at all.
If A, then B, else C.
I would prefer it if you took your shoes off.
I would be unhappy if you had not talked with me yesterday.
If I were you, I wouldn't go there alone.
If that's true, we had better get moving!
O what of Gods then boots it to be borne, / If old Aveugles ſonnes ſo euill heare?
Both Spear & Davis were indicted in the witchhunt surrounding the sensational "Revere sex ring."
He was a great friend, if a little stingy at the bar.
She won her team's admiration, if not its award, for her performance.
I don't know if I want to go or not.
Quoth Matthew, “ […] / She doubts if two and two make four, / […] ”
It is doubtful if the Victorian Londoner needed any warning, for the artful mobsmen, toolers, whizzers and dippers, together with their stickman accomplices, were everywhere in the crowds, in the underground, on railway trains […]
“Wait a minute!” said the girl: “I wouldn’t hurry by, if it was you that was coming out to be hung, the next time eight o’clock struck, Bill. I’d walk round and round the place till I dropped, if the snow was on the ground, and I hadn’t a shawl to cover me.”
If it’s the last thing I do / If it takes me from Tubilo to Timbuktu / If it’s the last thing I do / I’m gonna dodge every road block, speed trap, county cop / To get my hands on you / If it’s the last thing I do.
I have leftover cake if you want some.
noun
if (plural ifs)
(informal) An uncertainty, possibility, condition, doubt etc.
Examples
Sir Fran. Nay, but Chargy, if——— ¶ Miran. Nay, Gardy, no Ifs.——Have I refus'd three northern lords, two British peers, and half a score knights, to have put in your Ifs?
Well might Bergman add, , “if the compariſon that has been made, &c. be juſt.” The preſent writer makes no ifs about the matter, and has ſuperadded a little inaccuracy of his own, […]
Even if they managed to strike Japan, the United States or South Korea with nuclear weapons — a big if, given that they do not have a reliable delivery system — they could not save themselves from ultimate defeat.