Quantity is a generic term used when referring to the measurement (count, amount) of a scalar, vector, number of items or to some other way of denominating the value of a collection or group of items.

It is usually represented as a number (numeric value) of units together with the type of those units (if required) and a referent defining the nature of the collection. Both parts are required.

Examples are

• one apple, two apples, three apples, where the number is an integer so does not require a type
• 1.76 litres (liters) of milk
• 500 people

A number by itself is not a quantity, nor is a simple measurement. Where the unit count is one then the indefinite article may be used (for example, a car) and similar alternatives exist for other particular counts (for example, a brace of pheasant, a dozen eggs).

Quantification in its very simplest sense can be found in statements such as "A is greater than B". In the example cited, an expression is made that A has a greater quantity of something (such as volume or charisma) than B; and that if A and B were placed in an ordered set, then A would come after B if the order is arranged on an increasing (rather than decreasing) scale.