A regular pyramid's lateral faces are congruent isosceles triangles. The slant height of the regular pyramid is the altitude of any of **these triangles**. Since the altitudes of isosceles triangles are equal, the slant heights of regular pyramids are also equal.

The pyramid's base is the polygonal plane face, and its lateral faces are the triangular faces. The height (or altitude) of the pyramid is the perpendicular distance from the vertex to the plane of the base. A pyramid has n lateral faces if its base is a polygon with **n sides**. Because a triangle is a special case of a polygon with three sides, every pyramid has three mutually perpendicular faces.

Regular pyramids are ones where the base is a regular polygon (all sides and angles the same) of any number of sides. The simplest regular pyramid, then, is a 4-sided pyramid (base + 3 sides). An Egyptian pyramid has a square base and four triangular sides. There are many examples of pyramids in history other than those of Egypt. For example, the Pyramid of Giza in Egypt was built by Pharaoh Khufu.

There are also irregular or non-regular pyramids. These do not have **a regular base shape**. Instead, they can be any polyhedron with more than three faces (such as a triangulated sphere). Irregular pyramids were most likely used as tombs instead of regular ones since they could not be used for storing food or treasures. The only known ancient tomb of **this type** is that of Khenrenab near Xianyang in China.

However, there are some structures called "pyramids" that are not true pyramids (i.e., with a base equal to **their height**). Examples include **the Stepwell District** in India and Israel/Palestine. In these cases, the term "pyramid" is used because of their conical shape.

Finally, there are structures in some cultures with features resembling pyramids but without a clear apex (the top point), such as the Mound Builders' work in North America.

A pyramid is a polyhedron with triangle lateral sides that meet at a point and a polygon base. They are always named after the foundation. A rectangular pyramid can have a variety of cross sections. A perpendicular to the base cross section of a pyramid will be a triangle.

All pyramids have bases that are polygons with **three or more sides**. The sides of the base may be lines (linear) or they may be curved (circular). If the base has several parts then they are called fragments. A pyramid fragment is one side of the base cut off from the rest. A monolith is a large single stone kept in place by **its own weight**. The word is derived from Greek, meaning **single mass**. There are many monolithic structures around the world. Some famous examples include Stonehenge, Tikal, and Baalbek.

Pyramids were used as burial sites for important people during ancient times. They were also used as astronomical observatories because they reflect the sun's rays upon their slopes during certain times of the year. This causes shadows to fall upon some pillars inside the structure which serve as sundials for telling time.

There are many different types of pyramids including: mastabas (an Egyptian term for "sepulchre"), step pyramids, trihedral pyramids, and vaults. Mastabas are shaped like boxes with **flat tops** and are used for tombstones.

A pyramid is a polyhedron with **a polygonal base** and triangles on all lateral faces. It is one of **the two canonical forms** for a parallelipipedon the other being a cube.

Pyramids can be constructed by joining together pairs of triangular prisms, thus forming **a solid object** with an octahedral base. The apex of the pyramid is the highest point of the solid.

There are several types of pyramids: square, rectangular, triangular, and honeycomb.

The first three kinds are called regular, as they have **the same number** of edges and vertices. A regular pyramid has six equal sides and is named after the number of corners it has: tetrahedron (four corners), octahedron (eight corners). A honeycomb pyramid has no fixed dimensions but instead consists of an array of hexagonal cells connected by tubes.

An example of a regular pyramid is the Standard Pyramid, which has the same base area but different height depending on the dimension you choose to measure it in: 3 inches, 4 inches, or 5 inches. The top of the pyramid is flat and made of glass or stone. Scientists use pyramids to demonstrate **scientific principles** because they are easy to hold and visualize.