I need a simple rule/explanation for adult international students regarding the use of "were" rather than "was" when these verbs follow "If."
Thank you so much for any good tips that would aid in the students understanding of this rule.
In sentences which refer to a hypothetical or counterfactual situation, some people, especially speakers of AmE, prefer to use the subjunctive form of the verb. The only verb in English which has a different form for the past subjunctive is BE - were is used for all persons:
I wish I were rich. (I am not rich)
If Philo were here, he would explain it better than I (Philo is not here).
Many speakers of BrE use the indicative form - they would use was in those two sentences. Although some people claim that was is incorrect, most descriptive grammarians consider its use acceptable.
If you are interested in a long discussion on this, try: If I "were" king instead of "was"