The cube root of a number is the number whose cube is . It is also the edge length of a cube with a volume of . The cube root of is written as .

The cube root of 64 is written as . Its value is 4 because is 64. 

 is also the edge length of a cube that has a volume of 64. 

An irrational number is a number that is not rational. It cannot be written as a positive fraction, a negative fraction, or zero.

Pi () and are examples of irrational numbers.

The legs of a right triangle are the sides that make the right angle. 

Here are some right triangles. Each leg is labeled.

A rational number is a number that can be written as a positive fraction, a negative fraction, or zero. It can be written in the form where and are integers and is not equal to 0.

For example, 0.7 is a rational number because it can be written as .

Some examples of rational numbers: 

A repeating decimal has digits that keep going in the same pattern over and over. The repeating digits are marked with a line above them.

• The decimal representation for  is , which means 0.3333333 . . . .
• The decimal representation for is , which means 1.136363636 . . . .

The square root of a positive number is the positive number whose square is . It is also the side length of a square whose area is . The square root of is written as .

The square root of 16 is written as . Its value is 4 because is 16.

is also the side length of a square that has an area of 16.