can, could
(kan, kunde)

Can betyder att något är praktiskt eller teoretiskt möjligt.
Ex. 1: I work until 4 p.m. We can meet after that.
Ex. 2: Lisa cannot help you. She has no idea how to do it.

Could är preteritum (imperfekt/igår-formen) av can.
Ex. 1: I worked until 4 p.m. We could have meet after that.
Ex. 2: Was anybody able to help him?–Yes, Lisa could help him.