Possibility: might / may / could

Rules

• Rule 1: might / may / could + base verb

  After all three we use the base verb. They never take -s, and we don't use to. (In everyday American English might is the most common; may sounds a little more formal.)

  Pattern: subject + might / may / could + base verb

  Example: She might be at home.

  Example: We could win the game!

• Rule 2: Negative: might not / may not

  To say “perhaps not”, use might not or may not.

  Pattern: subject + might not / may not + base verb

  Example: I might not have time.

  Example: He may not know.

• Rule 3: Compare with will

  will = I'm sure. might / may = I'm not sure, maybe.

  Example: It will be sunny tomorrow. (sure)

  Example: It might be sunny tomorrow. (maybe)

• Rule 4: couldn't ≠ might not

  For possibility, couldn't means “impossible”. For “perhaps not”, use might not / may not.

  Example: It might not be true.

  Example: It couldn't be true! (impossible)

Common mistakes

• It might rains. → It might rain.

  After might, use the base verb.

• She mays come. → She may come.

  may never takes -s.

• I don't might go. → I might not go.

  Negative: might not (no don't).