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# Category:Numbers

A number is an abstract entity used to describe quantity. There are different types of numbers. The most familiar numbers are the natural numbers {0, 1, 2, ...} used for counting and denoted by N. If the negative whole numbers are included, one obtains the integers Z. Ratios of integers are called rational numbers or fractions; the set of all rational numbers is denoted by Q. If all infinite and non-repeating decimal expansions are included, one obtains the real numbers R. Those real numbers which are not rational are called irrational numbers. The real numbers are in turn extended to the complex numbers C in order to be able to solve all algebraic equations. The above symbols are often written in blackboard bold, thus:

$\mathbb{N}\sub\mathbb{Z}\sub\mathbb{Q}\sub\mathbb{R}\sub\mathbb{C}$

 Topics in mathematics related to quantity

## Subcategories

There are 10 subcategories to this category.

## Articles in category "Numbers"

There are 5 articles in this category.

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Last updated: 12-21-2004 10:16:39