If you find yourself debating whether to use “was” or “were” in a sentence, it’s likely that you’re dealing with an unreal conditional sentence. As a refresher, an unreal conditional sentence expresses events that are hypothetical or improbable.

Typically, an unreal conditional sentence begins with an if clause containing the past tense or past perfect tense of a verb followed by a conditional clause containing a modal verb such as “would.” Consider the following sentences:

If I had told you the answer, I would have been cheating. If I had run the race, I would feel accomplished.

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In both sentences above, the “if” clause contains a form of the past tense of the verb. There is one exception to this rule, however. If the verb in the if clause is “to be,” use “were,” even if the subject of the clause is a third person singular subject (i.e., he, she, it). See the examples below for an illustration of this exception:

If I was a rich man, I would make more charitable donations.

If I were a rich man, I would make more charitable donations.

If he was here right now, he would help us.

If he were here right now, he would help us.

Remember, though, that this exception applies only to unreal conditionals—that is, situations that do not reflect reality. (Hint: unreal conditionals often contain words like “would” or “ought to.”) When you’re talking about a possibility that did happen or might be true, use “was” and “were” as you normally would.

If I were rude to you, I apologize.