Could (verb)

1. Past tense of 'can'.
2. Used to indicate possibility or permission.
3. Used in making polite requests.

Origin:

Old english cūðe, past tense of cunnan (see can).

Examples:

1. I could swim when I was six.
2. We could go to the park if you want.
3. Could I borrow a pencil, please?
4. Could you pass me the salt?
5. Could you open the window, please?