In mathematics, when we introduce variables in expressions we might say, for example, "F=ma, for m the mass and a the acceleration." How would you translate the "for" here? Equivalently we could say "with m the mass...".
I was considering 以 or 为, with "F=ma,以质量m..." or "F=ma,质量为m...". If neither of these is appropriate, what is appropriate here?