The traditional statement about imperative clauses is that they express commands: they are for bossing people around, telling people what to do. This is not so. Imperatives express a much wider range of meanings, referred to in The Cambridge Grammar as directives. In today's Garfield cartoon strip (May 28, 2004) the difference comes out clearly.
"Nobody tells me what to do!", Garfield is thinking.
Then his owner/servant Jon appears with a heaped platter and says, "Have something to eat."
And the gluttonous cat says to himself, "Well, this is a bit awkward."
Not at all, Garfield. Tuck in. Jon's utterance is (syntactically) an imperative, but it is not (semantically) a command. It's just a directive. Directives can be polite invitations ("Come in"), suggestions ("Have a seat"), or even just good wishes ("Have a nice day!").
Posted by Geoffrey K. Pullum at May 28, 2004 05:16 PM