A DFA is a Finite State Machine where for each pair of state and input symbol there is one and only one transition to a next state.

The finite set of states includes an initial (start) state and a final state. It will take in a string of input symbols. It recognizes the set of regular languages and no other languages

A DFA is formally represented by the 5-tuple , where:

Q is a set of states.

Σ is a finite set of symbols, that we will call the alphabet of the language the automaton accepts.

δ is the state transition function

(δ : Q × Σ -> Q)

q0 is the initial state

F is the set of final states, subset of S

The above is an example for a DFA.