Automata
A deterministic automaton is

a graph with edges labeled by
items from a set of symbols called its alphabet

a single node designated the start state

a subset of nodes called accepting states
such that every node has at most one
edge from it labeled by any symbol.
There is also an implicit failure state
to which all edges not explicitly mentioned lead.
A possibly nondeterministic one may also
have edges labeled by a null symbol,
several start states, and several edges with the same
source and label.
