0 is a rational number. A rational number is defined as any number that can be expressed as the quotient of two integers, where the denominator is not zero. In this case, 0 can be represented as 0/1, 0/2, or any other fraction where the numerator is 0 and the denominator is a non-zero integer.
On the other hand, irrational numbers cannot be expressed as a simple fraction. These numbers have non-repeating, non-terminating decimal expansions. Examples of irrational numbers include √2 or π. Since 0 can be written as a fraction, it clearly fits the definition of a rational number.