The macro \frac add a gap (approx 1.2pt) before and after the whole fraction. You could compare




Even, the \genfrac command (setting the third arguement to "0pt") has still keep the gaps back:


though the horizontal rule is invisible.

The gaps takes some problems:

  1. If we use a huge font (e.g. set \fontsize to 20pt), the numerator/denominator does not match the fractional line in the projecting.
  2. If we write a binomial coefficient, the gaps are not necessity.

So, a customized command \newfrac without the gaps is beneficial.


TeX has a concept of a generalized fraction with delimiters. In case of \frac, there is a rule but no delimiters. Then TeX surrounds the fraction by a space of \nulldelimiterspace. Default is 1.2 pt.



  • Why \setlength{\nulldelimiterspace}{20pt}\binom{m}{n}\binom{m}{n} or \setlength{\nulldelimiterspace}{20pt}\genfrac{(}{)}{0pt}{0}{m}{n}\genfrac{(}{)}{0pt}{0}{m}{n}are invalid? – name abc Jun 26 '14 at 16:57
  • 1
    @nameabc: It is not invalid; \nulldelimiterspace is not used, because there are delimiters that are used instead. – Heiko Oberdiek Jun 26 '14 at 17:01
  • It should be noted that TeX uses one value of \nulldelimiterspace per formula, so one cannot change it in the middle of a formula. – egreg Jun 26 '14 at 17:13
  • 2
    One can change it in the middle of the formula but the last value is used for all fractions. – wipet Jun 26 '14 at 19:12

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.