Circle parts are important components of a circle, which is a two-dimensional shape with no beginning or end. The three main parts of a circle are SECTORS, arcs, and RADII. SECTORS are the parts of a circle that are created when a circle is divided into equal parts by a line. Arcs are curved lines that make up the circumference of a circle. RADII are the straight lines that connect the center of a circle to any point on its circumference.