An Automaton is a device which recognises or accepts certain elements of , where is a finite alphabet. Since the elements accepted by an automaton are a subset of , they form a language. Therefore each automaton will recognise or accept a language contained in . The language of consisting of the words accepted by an automaton is the language over accepted by and denoted by >
A deterministic automaton, denoted by , consists of a finite alphabet , a finite set of states, and a function called the transition function and a set of acceptance states.