Que signifie l'erreur: « Improper \spacefactor »? [FAQ LaTeX]

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---
section: The joy of TeX errors
permalink: /FAQ-atvert.html
date: 2014-06-10
---

# `\spacefactor` complaints

The errors
```latex
! You can't use `\spacefactor' in vertical mode.
\@->\spacefactor 
                 \@m 
```
or
```latex
! You can't use `\spacefactor' in math mode.
\@->\spacefactor 
                 \@m 
```
or simply
```latex
! Improper \spacefactor.
...
```
bite the LaTeX programmer who uses an internal command without
taking ''precautions''.  An internal-style command such as `foo`
has been defined or used in a private macro, and it is interpreted as
``, followed by the ''text'' `foo`.  (`` is used, for
real, to set up end-of-sentence space in some circumstances; it uses
`\spacefactor` to do that.)

The problem is discussed in detail in
''[`@` in macro names](FAQ-atsigns.md)'',
together with solutions.