Real number
A real number is a
number
that can be positive or negative and have decimal places after the point.
Example: 3.44, 56.1
Try this
Drag the orange dot below to move it along the number line
A real number is a value that represents any quantity along a
number line.
Because they lie on a number line, their size can be compared.
You can say one is greater or less than another, and do arithmetic with them.
Other kinds of numbers

Integers
Integers are numbers that have no decimal places or fractional parts.
See Integer definition.

Whole numbers (Counting numbers)
Whole numbers (or counting numbers)
are numbers that have no decimal places or fractional parts, and cannot be negative.
They are usualy used to count things, for example "12 students". In this use, a negative number of students does not make sense.
See Integer definition

Imaginary numbers
An imaginary number is a number whose square is negative. This can never happen with real numbers.
See Imaginary numbers.

Complex numbers
Just as real numbers lie on a number line, complex numbers can be plotted on a 2dimensional plane,
and each need a pair of numbers to identify them 
a real number and an imaginary number.
See Complex numbers
Animated definition of complex numbers and how they can be plotted on a twodimensional plane
An imaginary number is one that when squared, gives a negative result.
An overview of the types of numbers that are used in math. Links to other pages explaining each type in depth. Explains also that some numbers are not numbers at all.
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Other number topics
Scalar numbers
Counting numbers
Numbers that have factors
Special values
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