An ambiguous grammar is a context-free grammar for which there exists a string that has more than one leftmost derivation, while an unambiguous grammar is a context-free grammar for which every valid string has a unique leftmost derivation.
A regular grammar is a mathematical object, $G$, with four components, $G = (N, \Sigma, P, S)$, where
- $N$ is a nonempty, finite set of nonterminal symbols,
- $\Sigma$ is a finite set of terminal symbols, or alphabet, symbols,
- $P$ is a set of grammar rules, each of one having one of the forms:
- $A \rightarrow aB$
- $A \rightarrow a$
- $A \rightarrow \varepsilon$ for $A, B \in N$, $a \in Σ$, and $\varepsilon$ the empty string, and
- $S ∈ N$ is the start symbol.
Now the question is: Can a regular grammar also be ambiguous?