A funnel has three floors As you can see in the picture, the two points D and C are rotated once at equal distances from A and B , respectively, forming two homogeneous circular planes above and below the funnel , whose radii are AD and BC , respectively . The curved surface perpendicular to the ground along the circumference of the ground that surrounds the funnel is called the lateral surface of the funnel. The three sides of the funnel have two planes and one curve. References: The bottom of the funnel