A unit fraction is a fraction with numerator 1. Examples of unit fractions include 1/2, 1/3, 1/12, and 1/123456. The famous Rhind papyrus, dated to around 1650 BC, discusses unit fractions and contains a table of representations of 
as a sum of distinct unit fractions for odd n between 5 and 101. As a result, sums of unit fractions are now known as Egyptian fractions.
Calcus, Egyptian Fraction, Egyptian Number, Eye of Horus Fraction, Fermat-Catalan Conjecture, Half, Harmonic Number, Pandigital Fraction, Quarter, Scruple, Uncia
Wells, D. The Penguin Dictionary of Curious and Interesting Numbers. Middlesex, England: Penguin Books, pp. 29 and 31, 1986.