# Category:Numbers

A number is an abstract entity used to describe quantity. There are lots 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 vulgar 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:

[itex]\mathbb{N}\sub\mathbb{Z}\sub\mathbb{Q}\sub\mathbb{R}\sub\mathbb{C}[itex]
 Topics in mathematics related to quantity Numbers | Natural numbers | Integers | Rational numbers | Constructible numbers | Algebraic numbers | Computable numbers | Real numbers | Complex numbers | Split-complex numbers | Bicomplex numbers | Hypercomplex numbers | Quaternions | Octonions | Sedenions | Superreal numbers | Hyperreal numbers | Surreal numbers | Nominal numbers | Ordinal numbers | Cardinal numbers | p-adic numbers | Integer sequences | Mathematical constants | Large numbers | Infinity

## Articles in category "Numbers"

There are 0 articles in this category.

• Art and Cultures
• Countries of the World (http://www.academickids.com/encyclopedia/index.php/Countries)
• Space and Astronomy