A pleonasm is a device
that entails the use of a word superfluous
to the literal
meaning of a sentence, and which therefore could be deleted without affecting the sense of something. Pleonasms are more often used unintentionally than intentionally - "White Caucasian
" and "gay homosexual
" being two blatant examples of this.
However, they are used also to add emphasis to a word or phrase, with great efficacy, and can be found in almost all classic literature.
Language itself is geared towards their usage; most languages have an equivalent of the English "himself", as in "the man himself" (a common pleonasm), the word "autos" in Ancient Greek, for example. Homer used pleonasms extensively in The Iliad and The Odyssey, as in this extract:
Keito megas megalohsti.
He lay at his huge length. (Homer, Iliad 16.776)