A circle is a simple geometric shape defined as the set of all points in a plane that are equidistant from a central point, known as the center. The distance from the center to any point on the circle is called the radius. The total distance around the circle is called the circumference, which can be calculated using the formula C = 2\pi r, where r is the radius and \pi (pi) is a mathematical constant approximately equal to 3.14. Circles are commonly found in everyday life, from the shape of wheels to the design of coins. They are also significant in various fields, including mathematics, engineering, and art. In mathematics, circles are studied in relation to other shapes and concepts, such as circumference, diameter, and area, which can be calculated using the formula A = \pi r^2.