A circle is a simple shape in geometry that consists of all points in a plane that are the same distance from a central point, called the center. This distance is known as the radius. Circles are often seen in everyday life, such as in the shape of a pizza or a clock. Circles have special properties, including a constant ratio of the circumference (the distance around the circle) to the diameter (the distance across the circle through the center), known as pi (π). This unique relationship makes circles important in mathematics and engineering, as well as in art and design.