# Number Sets

## What does it mean?

### Definitions:

Natural Numbers - Common counting numbers.

Prime Number - A natural number greater than 1 which has only 1 and itself as factors.

Composite Number - A natural number greater than 1 which has more factors than 1 and itself.

Whole Numbers - The set of Natural Numbers with the number 0 adjoined.

Integers - Whole Numbers with their opposites (negative numbers) adjoined.

Rational Numbers - All numbers which can be written as fractions.

Irrational Numbers - All numbers which cannot be written as fractions.

Real Numbers - The set of Rational Numbers with the set of Irrational Numbers adjoined.

Complex Number - A number which can be written in the form a + bi where a and b are real numbers and i is the square root of -1.

## What does it look like?

A general example to help you recognize patterns and spot the information you're looking for

 Type of Number Example Natural Numbers $$N = 1, 2, 3, 4, ...$$ Prime Number $$P = 2, 3, 5, 7, 11, 13, 17, …$$ Composite Number $$4, 6, 8, 9, 10, 12, ...$$ Whole Numbers $$W = 0, 1, 2, 3, 4, …$$ Integers $$Z= …, -3, -2, -1, 0, 1, 2, 3, …$$ Rational Numbers $$Q = -\frac{1}{2}, 0.33333…, \frac{5}{2}, \frac{11}{10}, …$$ Irrational Numbers $$F = ..., \pi, \sqrt{2}, 0.121221222...$$ Real Numbers $$R = ..., -3, -1, 0, \frac{1}{5}, 1.1, \sqrt{2}, 2, 3, \pi , …$$ Complex Number $$C = ..., -3 + 2i, 0, 1 + 3i, …$$

## You'll use it...

Everyday. Numbers are included in all aspects of math.

## Video

### Number Sets

Watch a Khan Academy Video »
Length: 8:48