Non-literal language that describes one thing in terms of another - I am a rock; Blair is Bush's lapdog; ARGUMENT IS WAR.

A term or non-linguistic expression (such as a shrug of the shoulders) that expresses modality — The ice caps might have melted by the end of the century; You are certainly correct.

The feature of language that allows a speaker/writer to express certainty, desire or necessity — The Democrats might win the election; I wish there was world peace; You should vote in the election.

The words added to the head of a phrase to give further detail about the referent — Five cheeky monkeys in the zoo; The right and proper method for doing business.