## What is a number?

A **number** is a mathematical object that can be used for counting, measuring and labeling. The most original example of a number are the natural numbers as for example 1,2,3,4,5 and so on. Mostly used for counting and measuring, numbers are used for example as well for labels (i.e. telephone numbers), for ordering (serial numbers) and for codes such as for example ISBN's. In common usage number may often also refer to a symbol, a word or a mathematical abstraction.