Natural | 1, 2, 3, 4, 5, 6, 7, ... |
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Whole | 0,1, 2, 3, 4, 5, 6, 7, ... |

Integers | ..., -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, ..., |

Rational | Rational numbers look like fractions, a/b where a and b are integers and b is not zero |

Real | Real numbers include rational numbers, such as 4 and -2/9, irrational numbers, such as pi and the square root of two, and infinite decimals such as 3.465453339..., where the digits continue indefinitely. The real numbers are sometimes thought of as points on an infinitely long number line. |

Imaginary | An imaginary number is a number that when squared gives a negative result. The form bi where b is a non-zero, real number and i, defined by i^{2} = - 1, is known as the imaginary unit.
Imaginary numbers can be thought of as complex numbers where the real part is zero. |

Complex | A complex number is a number consisting of a real and imaginary part. It can be written in the form a + bi, where a and b are real numbers, and i is the standard imaginary unit with the property i ^{2} = -1. |