Ceci est une ancienne révision du document !

— title: `\spacefactor` complaints section: The joy of TeX errors date: 2014-06-10 —

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.