[Tex/LaTex] \begin{document} Undefined control sequence

lyx

I just have copied of Lyx files to one computer to another and i am facing above subjected problem. Complete log is given below.

This is pdfTeX, Version 3.1415926-2.4-1.40.13 (MiKTeX 2.9) (preloaded format=pdflatex 2012.12.19)  8 JAN 2013 21:37
entering extended mode
**chapter-1.tex
...
LaTeX Info: Redefining \ref on input line 87.
LaTeX Info: Redefining \pageref on input line 87.
LaTeX Info: Redefining \nameref on input line 87.
(C:\Users\Mani\AppData\Local\Temp\lyx_tmpdir.p11848\lyx_tmpbuf2\chapter-1.out) 
(C:\Users\Mani\AppData\Local\Temp\lyx_tmpdir.p11848\lyx_tmpbuf2\chapter-1.out)
\@outlinefile=\write3
! Undefined control sequence.
\@begindocumenthook ...ox {\autoref {##1}}}\addto 
                                                  \extrasenglish { \renewcom...
l.87 \begin{document}

The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

! Undefined control sequence.
\@begindocumenthook ...#1}}}\addto \extrasenglish 
                                                  { \renewcommand {\equation...
l.87 \begin{document}

The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
...

Best Answer

You need to add 

\usepackage[english]{babel}

(and perhaps other languages, according to your needs) to your document. Or remove whatever files that you are loading that depend on babel. \extrasenglish is a babel command used in customising document settings for English language use.

An interface to babel in the lynx GUI has been given by Torbjørn T. in the comments

Document --> Settings --> Language: Set Language pack.

Related Question