** Hans Hagen [2010-12-04 09:55:25 +0100]: [...]
\setupbodyfont[cambria]
\starttext This is a test. $a=\alpha$ $\bf a=\alpha$ $\bi a=\alpha$ \stoptext
BTW, I not sure if I use "correct" way to switch fonts in math mode (in LaTeX commands to switch fonts are different in text and math mode, and I have big LaTex background, so for me this way is unusual :).
best try to convert to the unicode math approach: bold a-z is different unicode slots than a-z and in context the \bf command does that transformation on ascii a-z (you can also key in the official unicode chars); the benefit is that you can cut and paste the bold characters in pdf files i.e. you retain that property; a bold b is not a bold one in typographic sense but a special symbol that happens to use a bold rendering; in for instance a section title, one can have all math bold, and then this regular bold character will become real bold But this is not universal solution.
Suppose I want to use serif bold italic font for vectors and sans bold italic for tensors (this is recommendation of NIST, see sp811.pdf on nist.gov). Of course I could enter vectors and tensors as symbols from appropriate unicode slots but what if my publisher says me that vectors should be in sans bold and tensors in serif bold italic? So I define commands, like \vect and \tensor to markup what symbols are verctors and what are tensors. Therefore I consider context (as well as LaTeX) as sort of markup (mix of procedural and descriptive markups). Returning to original question: I don't check but AFAIU one can define your own typescript and choose what fonts are used in math mode (mm?). If current typescript (modern?, latin modern?) doesn't have bold greek letters for math one should define new typescript and use for mm (math) font which have bold greek letters. P.S. I could be wrong with terms. --- WBR, Vladimir Lomov -- innovate, v.: To annoy people.