A number that can be made as a fraction of two integers (an integer itself has no fractional part).

In other words a/b is a rational number when a and b are numbers like -2 or 7 or 123. But be careful: b cannot be zero.

Examples:

• 1/2 is a rational number

• 0.75 is a rational number (3/4)

• 1 is a rational number (1/1)

• 2 is a rational number (2/1)

• 2.12 is a rational number (212/100)

• −6.6 is a rational number (−66/10)

There are numbers that cannot be written like that, such as π (pi), which is an "Irrational Number".

The word comes from "ratio" (not because they are rational thinkers or anything).