Hans Aberg
6. Juli 2015 11:03
Smallmatrix from AMS-TeX is not implemented in ConTeXt (Tex Live 2015), though crossed out in m-newmat.tex. I found this old post:
http://www.ntg.nl/pipermail/ntg-context/2005/013146.html

You can create your own matrix environment for inline use:

\definemathmatrix
  [smallmatrix]
  [left=\Big(,
   right=\Big),
   style=\scriptstyle,
   strut=0.7,
   distance=.25em]

\starttext

This is a example \m{ \startsmallmatrix \NC a \NC b \NR \NC c \NC d \NR \stopsmallmatrix } for a smallmatrix environment.

\stoptext

Wolfgang