Half

A half is a fraction written as 1/2, also expressed in decimal form as 0.5 and as a percentage as 50%. It represents one of two equal parts into which something has been divided. When an object is divided into two parts of equal size, each part is a half.

A half is the simplest fraction that is neither zero nor whole, and is one of the most commonly used fractions in everyday life. It appears in mathematics, measurement, commerce, and any division of something into two equal parts.

Forms of notation

A half can be written in three standard ways: as a fraction 1/2, as a decimal 0.5, and as a percentage 50%. All three are equivalent. There also exist equivalent fractions, such as 2/4, 3/6, and 50/100—all of which reduce to 1/2 when simplified.

Mathematical properties

When a number is multiplied by a half, the result is that number divided by two. For example: 10 × 0.5 = 5. When a number is divided by a half, the result is double that number: 10 ÷ 0.5 = 20. A half added to a half equals one (1/2 + 1/2 = 1). A half multiplied by a half equals one quarter (1/4).

Everyday use

A half appears in time measurement (half an hour = 30 minutes), in cooking measurements (half a cup), and in the division of property or resources. Somali has related terms, such as 'kala badh', meaning an equal division into two parts, and 'badhtan', referring to the middle or center.

Geometry and terminology

The concept of half underlies many scientific terms. For example, 'semicircle' is half a circle, where the diameter passes through the center. Similarly, Earth is divided into two halves (hemispheres) along lines of latitude.