A regular number, also called a finite decimal (Havil 2003, p. 25) is a positive number that has a finite decimal expansion. A number such as 
which is not regular is said to be nonregular. Nonregular numbers include repeating decimals and transcendental numbers.
The denominators of the first few regular unit fractions are 1, 2, 4, 5, 8, 10, 16, 20, 25, 32, 40, 50, ... (Sloane's A003592), which have decimal expansions 1, 
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Decimal Expansion, Repeating Decimal
Havil, J. Gamma: Exploring Euler's Constant. Princeton, NJ: Princeton University Press, 2003.
Sloane, N. J. A. Sequences A003592 in "The On-Line Encyclopedia of Integer Sequences." http://www.research.att.com/~njas/sequences/.