part of speech: auxiliary verb

definition 1: used to express that there was ability to do something in the past, or that an action or state was possible in the past.

  • My father could play tennis very well when he was young.

definition 2: used in present or future time to talk about some action or state that is possible but not certain; often used in polite requests or offers.

  • I could help you with it tomorrow, if you’d like.
  • Could I speak to the doctor, please?