A real variable is a symbol used in mathematics to represent a quantity that can take on any value within the set of real numbers. Real numbers include both rational numbers, like integers and fractions, and irrational numbers, such as √2 or π. Real variables are often denoted by letters like x, y, or z and are commonly used in equations and functions to model various phenomena. In calculus and algebra, real variables play a crucial role in understanding relationships between quantities. For example, in the function f(x) = x^2, x is a real variable that can take any real number, and the function describes how f changes as x varies. This concept is fundamental in fields such as physics, economics, and engineering, where real variables help describe continuous change.