A repetend is a term used in mathematics, specifically in the context of repeating decimals. It refers to the digit or group of digits in a decimal fraction that repeats indefinitely. For example, in the decimal representation of 1/3, which is 0.333..., the digit "3" is the repetend. In notation, the repetend is often indicated by placing a bar over the repeating digits. For instance, the decimal 0.666... can be written as 0.6̅, where the bar signifies that the "6" repeats forever. Understanding repetends is essential for converting repeating decimals into fractions and for various applications in number theory.