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:

See also

• WikiProject Numbers
• Category:Integers — containing the articles titled 1 (number), 2 (number), and so on

Subcategories

There are 12 subcategories to this category.

Cardinal numbers Complex numbers Constants D Dimensionless numbers

F Fractions I Irrational numbers L Large numbers Lists of numbers N Number sequences

N cont. Number stubs Numerical prefixes R Real numbers

Articles in category "Numbers"

There are 27 articles in this category.

Baker's dozen C Centered cube number Centered number D Decagonal number Dozen F Fraction (mathematics) H Heptagonal number Heptagonal pyramidal number Hypercomplex number

I Ionian numerals M Mythical number N Natural number Nominal number Nonagonal number Number O Octahedral number P Pentatope number Power of two Practical number

P cont. Preferred number R Round number S Shannon number Square number Star number T Table of divisors Table of prime factors Template:Numbers