The distance around a circle is called the circumference. The circumference is calculated using the formula C = 2πr, where "C" represents the circumference, "π" (pi) is a mathematical constant approximately equal to 3.14159, and "r" is the radius of the circle. This concept is crucial in geometry and is used in various practical applications, including engineering and construction. Knowing the circumference helps in understanding circular motion, designing circular objects, and determining distances traveled along curved paths.