How is a rational number defined?

A rational number is defined as a number that can be expressed as a fraction where both the numerator and the denominator are integers, and the denominator is not zero. This definition encapsulates all integers, fractions, and terminating or repeating decimals, demonstrating the wide range of values that rational numbers encompass.

For instance, the number 1/2 is a rational number because it can be expressed as the fraction of two integers. Similarly, the integer 5 can also be viewed as a rational number since it can be written as 5/1. This concept is foundational in understanding number sets, as rational numbers form an essential category within real numbers.

The other definitions do not accurately capture the essence of rational numbers. A number that cannot be written as a fraction refers to irrational numbers, such as π or the square root of 2. Whole numbers are a subset of rational numbers, but not all rational numbers are whole. Lastly, the statement about numbers being less than zero pertains to negative numbers, which include both rational and irrational numbers, but does not define rational numbers specifically.