Numbers

Numbers are mathematical objects used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, and so forth. Numbers can be classified into sets, called number systems, such as the natural numbers, integers, rational numbers, real numbers, and complex numbers.

History

The concept of number has been fundamental to the development of civilization. The first evidence of counting dates back to prehistoric finger and bone tallies. The first known system with place-value was the Mesopotamian base 60 number system (ca. 3400 BC) and the earliest known base 10 system dates to 3100 BC in Egypt.

Types of Numbers

Natural Numbers

Natural numbers are the set of all positive integers. They are the numbers we use for counting objects.

Integers

Integers are the set of all whole numbers, both positive and negative, including zero.

Rational Numbers

Rational numbers are numbers that can be expressed as a fraction where both the numerator and the denominator are integers.

Real Numbers

Real numbers include all the rational numbers, such as the integer −5 and the fraction 4/3, and all the irrational numbers, such as √2 (1.41421356..., the square root of two, an irrational algebraic number).

Complex Numbers

Complex numbers include all real numbers and the imaginary unit i, where i2 = −1.

See Also

• Number theory
• Number system
• Mathematics

Numbers Resources
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