(uncountable) A system for transferring messages from one computer to another, usually through a network.

(uncountable) A quantity of messages sent through an email system.

(countable) A message sent through an email system.

(countable, informal) An email address.

(obsolete, rare) Enamel (“an opaque, glossy coating”).

(transitive) To send an email or emails to.

(transitive, ditransitive) To send (something) through email.

(intransitive) To send, or compose and send, an email or emails.