Idiolect is an individual's unique use of language, including speech. This unique usage encompasses vocabulary, grammar, and pronunciation. This differs from a dialect, a common set of linguistic characteristics shared among a group of people.
The term is etymologically derived from the prefix idio-, from Ancient Greek ἴδιος, ídios, 'own, personal, private, peculiar, separate, distinct'; and -lect, abstracted from dialect, ultimately from Ancient Greek λέγω, légō, 'I speak'.