FatalCommands & Packages
Missing \endcsname
! Missing \endcsname inserted.
What this error means
\csname...\endcsname is used to construct command names dynamically. This error means \endcsname is missing or the content between \csname and \endcsname contains invalid characters (like spaces or non-letter tokens).
Common causes
- A \csname block was opened but \endcsname was not written
- Invalid characters (digits, spaces, or punctuation) inside a \csname block
- A label or reference containing special characters used in dynamic command construction
How to fix it
Ensure every \csname has a matching \endcsname. The name between them must contain only letters. If you need numeric or special characters in command names, escape or encode them first.
Code examples
Causes the error
\documentclass{article}
\begin{document}
% csname with space — invalid
\csname my command\endcsname
\end{document}Fixed
\documentclass{article}
\begin{document}
% csname with letters only
\csname mycommand\endcsname
\end{document}Related errors
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