A nonregular number, also called an infinite decimal, is a positive real number that has no terminating decimal expansion.
In contrast, a number that has a finite decimal
expansion such as 
is said to be regular.
Nonregular numbers include positive nonterminating repeating decimals and positive irrational numbers,
including positive transcendental numbers.
See also
Decimal Expansion,
Regular
Number,
Repeating Decimal
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References
Havil, J. Gamma: Exploring Euler's Constant. Princeton, NJ: Princeton University Press, 2003.Referenced
on Wolfram|Alpha
Nonregular Number
Cite this as:
Weisstein, Eric W. "Nonregular Number."
From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/NonregularNumber.html
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