Gerben Wierda via ntg-context schrieb am 19.05.2023 um 11:43:

I want to use a variable for a font size so I can set it based on language (as some translated texts have widely different sizes)

This fails:

%===========================

\newdimen\relationsFontSize
\relationsFontSize=8pt
\starttext
\switchtobodyfont[\relationsFontSize]
Hello, world!
\stoptext
%===========================

How can I use a variable to steer \switchtobodyfont size?

You need \the\<register>, i.e.

\switchtobodyfont[\the\relationsFontSize]

but I would use the measure command, e.g.

\definemeasure[relationsFontSize][8pt]
\starttext
\switchtobodyfont[\measure{relationsFontSize}]
Hello, world!
\stoptext

Wolfgang