In “Fiddler on the Roof,” Tevya sings, “If I were a rich man….” Why “were” and not “was”? We use “were” when the situation is not true, is contrary to fact. Tevya is poor. He wishes he were a rich man, but he knows he isn’t.
You’ve heard the expression, “If I were king….” But you’re not king, so again you use what is known as the subjunctive voice, using “were” instead of “was”:
“If I were taller, I would date taller women.” (He’s short.)
“If it weren’t snowing, we could go to the movies this afternoon.” (Not another blizzard!)
However, sometimes you want to use “was” instead of “were”; this is when the situation is not untrue:
“If I was talking too loudly, I’m sorry.” (You were blasting us out of the room.)
“If Andrea was at the rehearsal, I must have missed her.” (She was there; you were busy.)