gives the numerator of expr.
- Numerator picks out terms which do not have superficially negative exponents. Denominator picks out the remaining terms.
- An exponent is "superficially negative" if it has a negative number as a factor.
- The standard representation of rational expressions as products of powers means that you cannot simply use Part to extract numerators.
- Numerator can be used on rational numbers.
Introduced in 1988