Dear Otared, Am Samstag, den 04.06.2011, 23:59 +0200 schrieb Otared Kavian: > I think the error comes from your way of using \define: you use > \define\abs[1]{\lvert #1 \rvert} > instead of > \define[1]\abs{\lvert#1\rvert} > > the following works fine for me: > > \starttext > > %\define[1]\abs{|#1|} % this works > > \define[1]\abs{\lvert#1\rvert} % this works too > > $\abs{-1} = 1$ > \stoptext thank you very much for the solution. I took my definition from the Wiki [1]. Could the developers please clarify the correct syntax so that it can be updated in the source or the Wiki. Thanks, Paul [1] http://wiki.contextgarden.net/Reference/en/define