\begin{signature}\label{phase5_seed}
    %! infixl 2
    $X \phasefiveseed Y$ is a set.
\end{signature}

\begin{abbreviation}\label{phase5_alias}
    $\phasefivealias{X}{Y} = X \phasefiveseed Y$.
\end{abbreviation}

\begin{definition}\label{phase5_definition}
    $\phasefivedefinition{X}{Y} = \phasefivealias{X}{Y}$.
\end{definition}