a chord is a line segment and its endpoints are on the circle. a secant line is a "line" (meaning it is continuous and has no end points) that intersects a circle (in two places if that's not...
a sphere is a 3D circle like a ball 3D Items you can pick up they have three dimentions (they stand out) a circle is a 2D item like a pattern of circles 2D items have 2 dimentions (they're flat)