(Non)Deterministic Finite State Automata

• In a nondeterministic finite state automaton (NFA), there can be more than one edge originating from the same node and labelled with the same label.
• Or there can be a special $\epsilon$-edge, which can be followed without consuming any input symbols.
• By contrast, in a deterministic finite state automaton all edges leaving some node have pairwise disjoint label sets and there are no $\epsilon$-labels.