# [Tex/LaTex] Why are \colon and \mathpunct{:} not equivalent?

amsmathmath-mode

According to this answer, \colon is of type \mathpunct. But in the MWE below, the outputs of the two lines are not identical. Why not?

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{align*}
& g\colon X\to Y\\
& g\mathpunct{:} X\to Y
\end{align*}

\end{document}


1. The \mathpunct{} (without : inside {}) is the definition of \colon. Link1
2. Both : and \colon typeset a colon, but \colon is a punctuation symbol, while : is considered as a relation symbol as regards to spacing. Link2