Leftmost Derivation
During a leftmost derivation step, the leftmost nonterminal is rewritten.
Definition: Let G = (N, T, P, S) be a CFG, let
u Î T*, v Î (N È T)*. Let p = A ® x Î P be a rule. Then, uAv directly derives uxv in the leftmost way according to p in G, written as
uAv Þlm uxv [p]
Note: We define Þlm+ and  Þlm* by analogy with Þ+ and Þ*, respectively.
Gist:
12/50