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
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.