Is pi classified as a rational number or irrational number?

Pi is classified as an irrational number because it cannot be expressed as a fraction of two integers. An irrational number has a non-repeating, non-terminating decimal expansion. In the case of pi, its decimal representation begins with 3.14159 and continues indefinitely without repeating. This characteristic distinctly places pi outside the realm of rational numbers, which can be written as a quotient of integers and exhibit either terminating or repeating decimals.

In contrast, other classifications such as whole numbers, which are non-negative numbers without fractions or decimals, and terminating decimals, which are numbers that come to a complete stop after a finite number of digits, do not apply to pi. The uniqueness of pi's properties, particularly its infinite, non-repeating nature, firmly establishes its classification as an irrational number.