Common Number Sets

Natural Numbers

The whole numbers from 1 upwards. (Or from 0 upwards in some fields of mathematics). More ->

The set is {1,2,3,...} or {0,1,2,3,...}

Integers

The whole numbers, {1,2,3,...} negative whole numbers {..., -3,-2,-1} and zero {0}. So the set is {..., -3, -2, -1, 0, 1, 2, 3, ...}

(Z is for the German "Zahlen", meaning numbers, because I is used for the set of imaginary numbers). More ->

Rational Numbers

The numbers you can make by dividing one integer by another (but not dividing by zero). More ->

Q is for "quotient" (because R is used for the set of real numbers).

Examples: 3/2 (=1.5), 8/4 (=2), 136/100 (=1.36), -1/1000 (=-0.001), etc.

Algebraic Numbers

Any number that is a solution to a polynomial equations with rational coefficients.

Includes all Rational Numbers, and some Irrational Numbers. More ->

Real Numbers

All rational and irrational numbers. They can also be positive, negative or zero.

Includes the Algebraic Numbers and Transcendental Numbers.

A simple way to think about the Real Numbers is: any point anywhere on the number line (not just the whole numbers).

Examples: 1.5, -12.3, 99, √2, π

They are called "Real" numbers because they are not Imaginary Numbers. More ->

Imaginary Numbers

Numbers that when squared give a negative result.

If you square a real number you always get a positive, or zero, result. For example 2×2=4, and (-2)×(-2)=4 also, so "imaginary" numbers can seem impossible, but they are still useful!

Examples: √(-9) (=3i), 6i, -5.2i

The "unit" imaginary numbers is √(-1) (the square root of minus one), and its symbol is i, or sometimes j.

i² = -1

More ->

Complex Numbers

A combination of a real and an imaginary number in the form a + bi, where a and b are real, and i is imaginary.

The values a and b can be zero, so the set of real numbers and the set of imaginary numbers are subsets of the set of complex numbers.

Examples: 1 + i, 2 - 6i, -5.2i, 4