repetend

The repetend in the decimal form of a number is the set of numbers, if any, that are repeated indefinitely after the decimal point. For example, the rational number \(\frac{1}{7}\) is represented in decimal notation as \(0.142857142857\ldots\), or better as \(0.\overline{142857}\), and the digits 142857 are the repetend. (The line over the repretend is called the vinculum.)

Only rational numbers have repetends, and if we consider numbers with terminating decimals to have 0 (zero) as a repetend then being a rational number and having a repetend are equivalent conditions.