Definition

/ɛf/

noun

conjunction

Supposing that, assuming that, in the circumstances that; used to introduce a condition or choice.
“If it rains, I shall get wet.”
In 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 be unhappy if you had not talked with me yesterday.”