= Mathematical font constant
A \b[mathematical font constant] is a font-specific parameter used in <mathematical typesetting>. The `MathConstants` portion of an <OpenType MATH table> supplies distances, percentages and other parameters, including the <Math axis> offset and script scaling.<MATH - The Mathematical Typesetting Table by Microsoft>[MathConstants table; MathValueRecord]{ref}
For an invented distance example, suppose a <computer font> uses 1000 <font units> per <em> and specifies `fractionRuleThickness` as 40 <font units>. At 25 <pixels per em>, the ideal <typeset fraction> bar thickness is
$$
40\frac{25}{1000}=1\text{ pixel}.
$$
At 50 <pixels per em>, the same stored value gives 2 <pixels> before <rasterization> adjustments. A percentage value such as 80, however, is a ratio and must not be converted as though it meant 80 <font units>.
Keeping the units explicit prevents plausible-looking scale errors. Suggested values in the specification guide font design; they are not universal dimensions shared by every <computer font>.
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