Dear Aditya,
\startformula must occur inside a vbox. So, use a matrix environment as you are doing, or wrap the formula inside a \framed[align=normal].
Thank you for your solution. \framed[frame=off,align=normal]{\startformula\startalign ... \stopalign\stopformula} is working. I have two more questions. 1. In the output of the following code, 'x' in the first column is vertically centered, but matrix in the second column is not(located at top). What option can solve this? \starttable[|c|c|w4cm|w4cm|] \HL \NC A \VL B \VL C \VL D \NC\SR \HL \NC $x$ \VL \startmatrix \NC x' = \NC \NR \NC y' = \NC \NR \stopmatrix \VL \VL \NC\SR \HL \stoptable 2. In the output of the following code, the matrix in the second column is vertically centered, but 'x' in the first column is located at the bottom. \starttext \starttable[|c|c|w4cm|w4cm|] \HL \NC A \VL B \VL C \VL D \NC\SR \HL \NC $y$ \VL {\framed[frame=off, align=normal]{\startformula\startalign \NC x' = \NC \NR \NC y' = \NC \NR \stopalign\stopformula}} \VL \VL \NC\LR \HL \stoptable \stoptext Both of them are good for compiling, but need a slight touch. Would you please tell me how to set all columns vertical centered? Best regards, Dalyoung