Quantity
Categories: Elementary mathematics | Measurement
- For the use in linguistics, see length (phonetics).
Quantity is a general term used to refer to any type of quantitative property or attribute, such as mass, length, or time. A particular quantity is a magnitude of a scalar or vector quantity. The term quantity is also often used to refer to denumerable (countable) collections of objects.
A given quantity is usually represented either as a number of units, together with the type of those units, or a number of objects with a referent defining the type of object. Thus, Scalar quantities such as mass, and vector quantities such as force, are continuous quantities and are usually represented as a multiple of a real number and a unit of continuous quantity, such as a gram or newton. A count of a denumerable collection of entities is represented as an integer and the type of object or entity, such as an apple or a set. A number, including a particular measurement, is not by itself a quantity.
Examples are
- 1.76 litres (liters) of milk, which is continuous quantity
- <math>2 \pi r</math> metres, where r is the length of a radius of a circle expressed in metres (or meters)
- one apple, two apples, three apples, where the number is an integer representing the count of a denumerable collection of objects (apples)
- 500 people (also involving a count)
Where the 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.
See also:
eo:Kvanto fr:Quantité ko:양 (크기) hu:Mennyiség nl:Kwantiteit ja:量 simple:Quantity sv:Kvantitet