Hi Hans and Taco, amsmath.sty defines \lvert and \rvert which provide correct spacing when \vert is used as a left or a right delimiter (code at the end of email). I do not completely understand what amsmath is trying to do. Wouldn't \definemathsymbol [lvert] [open] [sy] ["6A] [ex] ["0C] \definemathsymbol [rvert] [close] [sy] ["6A] [ex] ["0C] this achieve the same goal? AMS code: % \subsection{Vertical bar symbols} % Add left/right specific versions of \cn{vert}, \cn{Vert}. Don't % assume the delimiter codes are the CM defaults. % \begin{macrocode} \def\@tempa#1#2\@nil{% \ifx\delimiter#1\@tempcnta#2\relax\else\@tempcnta\z@\fi } \@xp\@tempa\vert\@empty\@nil \ifnum\@tempcnta>\z@ \advance\@tempcnta "4000000 \xdef\lvert{\delimiter\number\@tempcnta\space } \advance\@tempcnta "1000000 \xdef\rvert{\delimiter\number\@tempcnta\space } \else \ifx\@@undefined\lvert % Fall back to cmex encoding since we don't know what else to do. \DeclareMathDelimiter{\lvert} {\mathopen}{symbols}{"6A}{largesymbols}{"0C} \DeclareMathDelimiter{\rvert} {\mathclose}{symbols}{"6A}{largesymbols}{"0C} \fi \fi \@xp\@tempa\Vert\@empty\@nil \ifnum\@tempcnta>\z@ \advance\@tempcnta "4000000 \xdef\lVert{\delimiter\number\@tempcnta\space } \advance\@tempcnta "1000000 \xdef\rVert{\delimiter\number\@tempcnta\space } \else \ifx\@@undefined\lVert \DeclareMathDelimiter{\lVert} {\mathopen}{symbols}{"6B}{largesymbols}{"0D} \DeclareMathDelimiter{\rVert} {\mathclose}{symbols}{"6B}{largesymbols}{"0D} \fi \fi Aditya