1\documentclass{article} 2\newcommand{\mysection0}{\section{#1}} 3\newcommand{\mysection1}[1]{\section{#1}} 4\newcommand{\mysection2}[1][1]{\section{#1}} 5\newcommand\mysection3[1][1]{\section{#1}} 6\renewcommand{\foo}{\section{#1}} 7\providecommand{\bar}{\section{#1}} 8\def\baz{\section{#1}} 9\DeclareMathOperator{\op}{foo} 10\begin{document} 11\mysection0{ABC} 12\mysection1{EFG} 13\mysection2{HIJ} 14\end{document} 15