A repeating decimal is a decimal number that has a digit or a group of digits that repeat infinitely. For example, the fraction 1/3 equals the decimal 0.333..., where the digit "3" continues forever. This can also be represented as 0.3̅, indicating that the "3" repeats. Repeating decimals can arise from dividing integers, particularly when the denominator has prime factors other than 2 or 5. They can be converted back into fractions. For instance, 0.666... is equivalent to the fraction 2/3. Understanding repeating decimals is essential in mathematics for precise calculations.