Writing positive rational numbers as the sum of fractions with all numerators equal to one.

Writing positive rational numbers as the sum of fractions with all numerators equal to one, i.e. $\frac1n$. The denominators are usually required to be distinct.

So, for example, $1=\frac12+\frac13+\frac16$.

See Wikipedia:Egyptian Fraction and Mathworld:Egyptian Fraction for more information.