One-fifth is a fraction that represents one part out of five equal parts of a whole. It is written as 1/5 and can also be expressed as a decimal, which is 0.2. This means that if you divide something into five equal sections, one-fifth would be one of those sections. In practical terms, if you have a pizza cut into five equal slices, taking one slice means you have one-fifth of the pizza. This concept is commonly used in mathematics, cooking, and everyday situations where division into equal parts is necessary, such as sharing food or money.