Pyramid

A pyramid is a polyhedron, which consists of a flat polygon - the base of the pyramid , a point not lying in the plane of the base - the top of the pyramid and all segments connecting the top of the pyramid with the points of the base. The segments connecting the top of the pyramid with the vertices of the base are called lateral edges .
A1A2A34 - the base of the pyramid, S - the top of the pyramid, A1S, A2S, A3S, A4S - the edges of the pyramid.
The height of the pyramid is called perpendicular, lowered from the top of the pyramid on the plane of the base.