A rational number is a number that can be expressed as the quotient or fraction of two integers, where the denominator is not zero. In other words, it is a number that can be written in the form p/q, where p and q are integers and q is not equal to zero. Rational numbers include integers, which can be written as a quotient with the integer as the numerator and 1 as the denominator. Rational numbers can be positive, negative, or zero.

Examples of rational numbers include:

• 1/2
• 3/4
• -5/6
• 0.45 (since it can be written as 45/100)
• Every natural number (since it can be expressed as a fraction with 1 as the denominator)
• Every integer number (since it can be expressed as a fraction with the integer as the numerator and 1 as the denominator)

On the other hand, numbers that cannot be expressed as a quotient of two integers are called irrational numbers. Examples of irrational numbers include the square root of 2, pi, and e.