Label Multiply Defined

What this error means

Two \label{} commands in your document use the same identifier. LaTeX will use the value from the second definition, which may cause wrong cross-references. This is a warning, not an error, but the output will likely be incorrect.

Common causes

• The same label string used in two different \label{} calls
• Copying a section and forgetting to rename its label
• Multiple included files each defining a label with the same name

Code examples

\documentclass{article}
\begin{document}

\section{Introduction}\label{sec:intro}
% ...
\section{Background}\label{sec:intro}  % Duplicate!

\end{document}

\documentclass{article}
\begin{document}

\section{Introduction}\label{sec:intro}
% ...
\section{Background}\label{sec:background}  % Unique label

\end{document}

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