A **fraction** is a number that can represent part of a whole.
The earliest fractions were reciprocals of integers: ancient symbols representing one part of two, one part of three, one part of four, and so on. A much later development were the common or "vulgar" fractions which are still used today (½, ⅝, ¾, etc.) and which consist of a **numerator** and a **denominator**, the numerator representing a number of equal parts and the denominator telling how many of those parts make up a whole.
An example is 3/4, in which the numerator, 3, tells us that the fraction represents 3 equal parts, and the denominator, 4, tells us that 4 parts make up a whole. Fractions can also represent divisions. eg, 2 ÷ 3 can be written as a fraction. This would become ⅔.

A still later development was the decimal fraction, now called simply a decimal, in which the denominator is a power of ten, determined by the number of digits to the right of a decimal separator, the appearance of which (e.g., a period, a raised period (•), a comma) depends on the locale. Thus for 0.75 the numerator is **75** and the denominator is 10 to the second power, *viz.* **100**, because there are two digits to the right of the decimal.

A third kind of fraction still in common use is the percentage, in which the denominator is always 100. Thus 75% means 75/100.

Other uses for fractions are to represent ratios, and to represent division. Thus the fraction 3/4 is also used to represent the ratio 3:4 (three to four) and the division 3 ÷ 4 (three divided by four).

In mathematics, the set of all (vulgar) fractions is called the set of rational numbers, and is represented by the symbol **Q**.