Editing Ambiguous grammar (section)

=== Trivial language ===
The simplest example is the following ambiguous grammar (with start symbol A) for the trivial language that consists of only the empty string:
: A → A | ε
... meaning that the nonterminal A can be derived to either itself again, or to the empty string. Thus the empty string has leftmost derivations of length 1, 2, 3, and indeed of any length, depending on how many times the rule A → A is used.

This language also has an unambiguous grammar, consisting of a single [[Production rule (formal languages)|production rule]]:
: A → ε
... meaning that the unique production can produce only the empty string, which is the unique string in the language.

In the same way, any grammar for a non-empty language can be made ambiguous by adding duplicates.