A production is composed of two kinds of elements: terminals and nonterminals. A terminal is a character literal (e.g., "A"). A non-terminal is a reference to another production. This reference occurs through a name, which appears to the left of a separator (::=) in a production. To the right of a separator appear the allowed terminals and non-terminals for the production. Consider a hypothetical language composed of variable-length sequences of the lowercase letter "a". Such a language could be cast as the following two productions: