area of the base

A regular pyramid is one whose base is a regular polygon whose center coincides with the foot of the perpendicular dropped from the vertex to the base.
 

A pyramid is a polyhedron with a polygon base of any shape, and all other faces are triangles which have common vertex.
 

A right circular cylinder is a cylinder whose base is a circle and whose elements are perpendicular to its base.
 

Cylinder is a solid bounded by a closed cylindrical surface and two parallel planes.
 

Prism is a polyhedron in which two faces are equal polygons in parallel planes, and all other faces are parallelograms. There are two types of prism; oblique prism and right prism. Oblique prism is when the axis is not perpendicular to the base and right prism if the axis is parallel to the base. In right prism, all lateral areas are rectangle.