Whenever there is a derivation with G such that: there is, by definition, a sequence of transitions with M such that: (where q i ∈ Q, a i ∈ Σ∪{ }, a ∈ Σ * , b i ∈ ∆∪{ } and b ∈ ∆ * for all i) and the state X n is by definition a member of F .
: whenever G generates ab ← , M can recognize a, b .