if

Supposing that, assuming that, in the circumstances that; used to introduce a condition or choice.

“If it rains, I shall get wet.”

“I'll do it next year —if at all.”

computingIn the event that a statement is true (a programming statement that acts in a similar manner).

“If A, then B, else C.”

Supposing that; used with past or past perfect subjunctive indicating that the condition is closed.

“I would prefer it if you took your shoes off.”

“I would be unhappy if you had not talked with me yesterday.”

Supposing that; given that; supposing it is the case that.

“If that's true, we had better get moving!”

Although; used to introduce a concession.

“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.”

sometimes proscribedWhether; used to introduce a noun clause, an indirect question, that functions as the direct object of certain verbs.

“I don't know if I want to go or not.”

usually hyperbolicEven if; even in the circumstances that.

Introducing a relevance conditional.

“I have leftover cake if you want some.”

informalAn uncertainty, possibility, condition, doubt etc.