Difference Between DFA and NFA

There is not much difference between DFA and NFA because they both accept regular languages. The basic difference in both of these is their transition function is different. 

  • In DFA, The transition function (δ) takes two arguments (state, symbol) as input and returns a single state as output.
  • In NFA, The transition function (δ) takes two arguments (state, symbol) as input and can return multiple states.

The following picture explains the differences in both DFA and NFA.

Difference between DFA and NFA

Difference between DFA and NFA

The top 10 differences in DFA and NFA are listed below,

SR NO. DFA NFA
1 DFA stands for Deterministic Finite Automata. NFA stands for Nondeterministic Finite Automata.
2 For each sigma value (0, 1…n) there must be a provided path from each state. For each sigma value (0, 1…n), there is no need to specify the path from each state
3 DFA provides a path for each input, so all digital computers are deterministic. NFA does not provide a path for each input, so NFA is not used in digital computers.
4 There is only one possible transition from one state on the one input symbol. It means multiple choices corresponding to an input are not available. There is more than one possible transition from one state on the same input symbol. It means multiple choices are available corresponding to a single input.
5 DFA cannot use Empty String. (Epsilon) transition. NFA can use an Empty String (Epsilon) transition.
6 DFA is more difficult to construct and understand. NFA is easier to construct and understand.
7 All DFA are NFA. All NFA are not DFA.
8 DFA requires more space. Because it has normally more states. NFA requires less space than DFA. Because it usually has fewer states
9 Dead State does not in DFA  Dead State may exist in NFA 
10 Trap State is used in DFA Trap State is not used in DFA

Important points:

  • While converting NFA to DFA, If the NFA maximum states are n, Then the DFA maximum number of states will be 2n.
  • NFA and DFA both can hold more than one final states