TeX/above
Synopsis
\above[dimen]
Description
\above is TeX's more general command for making fractions. Printing
a\above 0.5pt b
produces the fraction where the separating bar has thickness 0.5pt. Grouping may be required to make sure that not too much is included in the numerator and denominator. A good rule of thumb is to simply put braces around any fraction as in
{a\above 0.5pt b}
The primitives \over and \atop can be replicated in terms of \above as
\over = \above 0.4pt \atop = \above 0pt