Number - Classification of Numbers

Classification of Numbers

See also: List of types of numbers

Different types of numbers are used in many cases. Numbers can be classified into sets, called number systems. (For different methods of expressing numbers with symbols, such as the Roman numerals, see numeral systems.)

Important number systems
Natural 0, 1, 2, 3, 4, ... or 1, 2, 3, 4, ...
Integers ..., −5, −4, −3, −2, −1, 0, 1, 2, 3, 4, 5, ...
Rational a⁄b where a and b are integers and b is not zero
Real The limit of a convergent sequence of rational numbers
Complex a + bi where a and b are real numbers and i is the square root of −1

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