Used in the first clause of a sentence to state a fact as a premise for a conclusion, often followed by 就 jiù or 那么 nà​me

there is; there are; to exist; to occur or happen

currently; now; the present time

Used in rhetorical questions to suggest that something is unnecessary or that there is no reason to do it; why must; why should.

at that time; at the outset; originally, especially referring to when a particular event first took place