\begin{frame}
\small

\begin{definition}
\smallskip
\begin{itemize}
\item
\makebox[10mm][l]{\alert<1,2>{$p < q$}} 
\makebox[30mm][l]{if $\exists\,r \neq \epsilon\colon p r = q$} 
``$p$ is \alert<1,2>{strictly above} $q$''
\quad
``$q$ is \alert<1,2>{strictly below} $p$''
\item<3->
\makebox[10mm][l]{\alert<3>{$p \leqslant q$}} 
\makebox[30mm][l]{if $\exists\,r\colon p r = q$} 
``$p$ is \alert<3>{above} $q$''
\quad
``$q$ is \alert<3>{below} $p$''
\item<4->
\makebox[10mm][l]{\alert<4-6>{$p \parallel q$}}
\makebox[30mm][l]{if $p \nleqslant q$ and $q \nleqslant p$} 
``$p$ and $q$ are \alert<4-6>{parallel}''
\end{itemize}
\end{definition}

\bigskip

\begin{example}<2->
\qquad\GREEN{\begin{tikzpicture}[on grid,baseline=(1).baseline]
\matrix[ampersand replacement=\&,row sep=5mm,column sep=2mm]{
\& \& \& \node (1) {$\epsilon$}; \& \& \& \\
\& \node (2) {$\alert<5,6>1$}; \& \& \& \& \node (3) {$\alert<2,5>{2}$};
\& \\
\node (4) {$11$}; \& \& \node (5) {$12$}; \& \& \node (6) {$21$}; \& \&
\node (7) {$22$}; \\
\& \& \node(10) {$121$}; \& \node (8) {$\alert<2>{211}$}; \& \&
\node (9) {$\alert<6>{212}$};
\& \\};
\draw (1) -- (2) (1) -- (3);
\draw (2) -- (4) (2) -- (5) (5) -- (10);
\draw (3) -- (6) (3) -- (7);
\draw (6) -- (8) (6) -- (9);
\end{tikzpicture}}
\quad
\begin{minipage}[t]{2cm}
\begin{itemize}
\item<2->
\alert<2>{$2 < 2 1 1$}
\item<5->
\alert<5>{$1 \parallel 2$}
\item<6->
\alert<6>{$1 \parallel 2 1 2$}
\end{itemize}
\end{minipage}
\end{example}

\end{frame}