All, This is fine. \starttext \startformula \left(\matrix{y_1\cr y_2\cr \vdots\cr y_n}\right)= \left(\matrix{x_1^2\cr x_2^2\cr \vdots\cr x_n^2}\right) -2\left(\matrix{x_1\cr x_2\cr \vdots\cr x_n}\right) -\left(\matrix{3\cr 3\cr \vdots\cr 3}\right). \stopformula If \startformula \vec x =\left(\matrix{x_1\cr x_2\cr \vdots\cr x_n}\right)\quad\hbox{and}\quad \vec y =\left(\matrix{y_1\cr y_2\cr \vdots\cr y_n}\right), \stopformula \stoptext But when I redefine \vec, I get a problem. \def\vec#1{\bf #1} \starttext \startformula \left(\matrix{y_1\cr y_2\cr \vdots\cr y_n}\right)= \left(\matrix{x_1^2\cr x_2^2\cr \vdots\cr x_n^2}\right) -2\left(\matrix{x_1\cr x_2\cr \vdots\cr x_n}\right) -\left(\matrix{3\cr 3\cr \vdots\cr 3}\right). \stopformula If \startformula \vec x =\left(\matrix{x_1\cr x_2\cr \vdots\cr x_n}\right)\quad\hbox{and}\quad \vec y =\left(\matrix{y_1\cr y_2\cr \vdots\cr y_n}\right), \stopformula \stoptext I thought \vec in this case should just chew up the very next symbol, but the bold seems to continue into the display in the second formula. I'm missing something here. What is it?