Dear list, For reference here some old thread on the same(?) topic. https://mailman.ntg.nl/pipermail/ntg-context/2017/088699.html https://mailman.ntg.nl/pipermail/ntg-context/2017/088747.html https://mailman.ntg.nl/pipermail/ntg-context/2017/088926.html I noticed, that the placement of the prime now depends on the placement in the source code. If I write \omega_n' the prime is placed in the exponent of the whole \omega_n atom rather than just the \omega atom. MWE is below. At the same time, I do not see why the Plain TeX behaviour of an active prime in mathmode was abandoned, because if I simply backport this, everything seems to work fine. Cheers, Henri --- \starttext \startformula \omega_n' \neq \omega'_n \stopformula % --- \catcode`@=11 % from plain.tex \mathcode`\'="8000 % ^\prime {\catcode`\'=\active \gdef'{^\bgroup\prim@s}} \def\prim@s{\prime\futurelet\next\pr@m@s} \def\pr@m@s{\ifx'\next\let\nxt\pr@@@s \else\ifx^\next\let\nxt\pr@@@t \else\let\nxt\egroup\fi\fi \nxt} \def\pr@@@s#1{\prim@s} \def\pr@@@t#1#2{#2\egroup} \startformula \omega_n' = \omega'_n \stopformula \stoptext