Editing Chomsky normal form (section)

=== Chomsky reduced form ===
Another way<ref name="Hopcroft.Ullman.1979"/>{{rp|92}}<ref>Hopcroft et al. (2006){{page needed|date=November 2014}}</ref> to define the Chomsky normal form is:

A [[formal grammar]] is in '''Chomsky reduced form''' if all of its production rules are of the form:
: <math>A \rightarrow\, BC</math> or
: <math>A \rightarrow\, a</math>,
where <math>A</math>, <math>B</math> and <math>C</math> are nonterminal symbols, and <math>a</math> is a [[terminal symbol]].  When using this definition, <math>B</math> or <math>C</math> may be the start symbol.  Only those context-free grammars which do not generate the [[empty string]] can be transformed into Chomsky reduced form.