The set of rational numbers, represented by the symbol $\mathbb{Q},$ is formed by all numbers that can be expressed as the ratio between two integers, $\frac{a}{b},$ where $b\ne 0.$ All four of these examples are rational numbers. Note that integers are also rational because they can always be written as fractions with a denominator of $1.$ In other words, integer numbers is a subset of rational numbers.

Real numbers that are not rational are called irrational numbers.