Definition of "if"
Supposing that, assuming that, in the circumstances that; used to introduce a condition or choice.
Supposing that; used with past subjunctive indicating that the condition is not fulfilled.
Although; used to introduce a concession.
In the event that a statement is true (a programming statement that acts in a similar manner).
Whether; used to introduce a noun clause as the object of certain verbs.
Even if; even in the circumstances that.
An uncertainty, possibility, condition, doubt etc.