What does the term real numbers include?

The term "real numbers" is defined to encompass both rational and irrational numbers. Rational numbers include any numbers that can be expressed as a fraction where the numerator and denominator are integers (with the denominator not being zero). This category covers integers, whole numbers, and fractions. On the other hand, irrational numbers are those that cannot be expressed as a simple fraction, meaning they cannot be represented as a ratio of two integers. Examples include the square root of non-perfect squares (like √2) and mathematical constants such as π (pi).

By stating that real numbers include all rational and irrational numbers, the definition showcases the complete nature of the real number line, which comprises every possible numerical value that can represent a distance along a continuous line. Thus, the correct choice reflects the comprehensive nature of the real number system. This clarity in understanding is crucial for foundational concepts in mathematics related to number theory and allows for advanced exploration of functions, algebra, and calculus, where both types of numbers frequently intersect.