Hello, everyone: This is a recording from a native American teacher: The difference between cap and lid is that a cap usually seals on something. For example, in pictures(link2) 2 and 3 the cap seals on the bottle. You must unscrew it to take it off. A lid just covers something. Lid and cover can be used interchangeably. They mean the same thing. 1. a cap usually seals on something. 2. a cap usually seals something. WR dictionary says "seal" is transitive, so I think #1 is incorrect and #2 is correct. Am I right? Thank you.