if

/ɪf/

#35 of the most-used English words

noun

1. An uncertainty, possibility, condition, doubt etc.

conjunction

1. Supposing that, assuming that, in the circumstances that; used to introduce a condition or choice.
   "If it rains, I shall get wet."
2. In the event that a statement is true (a programming statement that acts in a similar manner).
   "If A, then B, else C."
3. 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."
4. Supposing that; given that; supposing it is the case that.
   "If that's true, we had better get moving!"