The example below shows the intended output when using original TeX code (compiled with ‘context' of TeX Live 2015): a pair of left braced formulas. The first comment shows what works in AMS-LaTeX. However, when trying similar ConTeXt commands, I get the error shown in the comment below. What ConTeXt command might use here? --- \setupformulas[location=left] \starttext \def\equlb#1{\left\{\eqalign{#1}\right.} %equation left braced % AMS-LaTeX %\def\equlb#1{\left\{ \begin{aligned} #1 \end{aligned}\right.} % equation left braced % ConTeXt error: You can't use `\halign' in math mode. %\def\equlb#1{\left\{ \startalign #1 \stopalign\right.} %\def\equlb#1{\left\{ \startmathalignment #1 \stopmathalignment\right.} \startformula \placeformula[JcoordDef] J^j:\equlb{ω^0 &→ 0 \cr ω^j &→ 0} \quad \equlb{ω^k &→ ω^l \cr ω^l &→ -ω^k} \stopformula \stoptext ---