Was, should be, or would be, able, capable, or susceptible. Used as an auxiliary, in the past tense or in the conditional present.
- Used to indicate ability or permission in the past: I could run faster then. Only men could go to the club in those days.
- Used with hypothetical or conditional force: If we could help, we would.
- Used to indicate tentativeness or politeness: I could be wrong. Could you come over here?