temp.tex<2>

    A language $L$ with $L \subseteq \Sigma^*$ is regular exactly if:
    \begin{itemize}
  \item $L = \{a\}$ with $a \in \Sigma$
  \item $L = \emptyset$
    \end{itemize}
    or
    \begin{itemize}
  \item $L = L_1 \cdot L_2 $
  \item $L = L_1 \cup L_2 $
  \item $L = L_1^*$
    \end{itemize}

    Alternative Definition:
    \begin{itemize}
  \item it can be accepted by a finite automaton
  \item it can be generated by a regular grammar
  \item it can be generated by a regular expression
    \end{itemize}