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A very common grammatical error is the misuse of “may and might”. Today in colloquial (casual) English, “might” is used for both. But that is not grammatically correct. A little grammatical background is in order.

Both ‘may and might” only express action or actions that are “possible”, but not “definite”, e.g., I think I may go to the movies this afternoon (not definite, but only “possible” action). I thought I might go to the movies last night (not definite, but only “possible” action on the day before).

“May and might” can only state possible action, and “possible action” in grammar is called the “Subjunctive Mood”. Wow. That’ll scare you!

On the other hand, to express “definite action”, is called the “Indicative Mood” in grammar.

The verb, therefore following “may and might” is no longer in the “Indicative Mood”, (definite action), but rather in the “Subjunctive Mood”, (possible action).

RULES:

1. If the main verb of the sentence is either in the present tense or future tense, “may” must be used, (I think (or will think) I may go to the movies this afternoon). “Go” is in the “Subjunctive Mood” because “may” made the action only possible.

2. If the main verb of the sentence is in any other tense, “might” must be used, (I thought I might go to the movies last night). Here, “go” is also in the “Subjunctive Mood” because “might” made the action only possible.

Many students say that they do not understand the “Subjunctive Mood”,  but the RULE S are so simple:

Definite action = the “Indicative Mood”; Possible action = the “Subjunctive Mood”. That is all that is necessary to understand how the “Subjunctive Mood” works in English grammar. It is a carry-over from Latin. It’s not difficult at all to understand the difference between “definite action” and “possible action”.

We can call, therefore, “may and might” Subjunctive Mood triggers in English grammar.