Pyramids are classified into several categories based on the geometry of **their bases**. Square Pyramid Triangular Pyramid Pyramid of the Pentagon Pyramid on the right. Pyramid, oblique-angled from **all sides** (not just one angle). Based on a triangle with three equal sides.

The word "pyramid" comes from Greek πύραμά τ' έπος, which means "firestone" or "brick". It was first used by Ancient Egyptians to refer to a stone structure used as a tomb marker or roadside shrine. The Greeks later adopted this term and used it for any tower-like structure made of baked clay or stone. Through history, many rulers have used the services of architects to design huge pyramid structures as monuments to themselves. These structures usually include two opposite angles that are exactly parallel to each other. At the top, these angles join together to form a perfect triangle.

There are several different types of pyramids. They are generally categorized by the shape of **their base**. The most common types are the square pyramid and the triangular pyramid. There are also quadrilateral (four-sided) and polygonal (many-sided) pyramids. Although less common, there is also a pentagonal pyramid and a hexagonal pyramid.

A triangular pyramid, a pentagonal pyramid, and a hexagonal pyramid are three further varieties of pyramids, all called by the shape of their bases. The sides of **a right pyramid** are isosceles triangles, which have **two equal sides** and angles. There are also two other pyramid shapes: a square pyramid with four equal sides and a circular pyramid with no fixed dimensions but having a constant radius of curvature.

Isosceles means "equal-sided," and this describes the two sides of a right isosceles triangle. Because both sides are identical, they can never be measured individually; only the overall size can be determined. The two angles opposite each side are equal, as are the two angles opposite the front and back edges. Isosceles triangles are common in nature; for example, the human skull is mostly made up of these triangles. Isosceles triangles are divided into two categories: scalene and obtuse-scalene. A scalene isosceles triangle has three unequal angles, while an obtuse-scalene triangle has one angle that is very large compared to the others.

Right triangles are very important in mathematics because many concepts in geometry can be expressed in terms of **right triangles**.

A pyramid is a polyhedron with a polygonal base and triangles on all of **its lateral faces**. There are, however, various sorts of pyramids. The form of a pyramid's base is often used to characterize it. A triangular pyramid, for example, has a triangle foundation, while a hexagonal pyramid has a hexagonal base. All pyramids have triangular faces, but not all triangular pyramids are true pyramids.

The concept of a pyramid with non-triangular bases has come up in the history of mathematics. There are two sorts of square pyramid: one with squares as its base and another with rhombs as its basis. Neither of these is considered a true pyramid because it lacks a triangular face. Similarly, there are also double pyramids with diagonals equal to each other and vertices that are symmetric with respect to both the x-axis and y-axis. These too are not true pyramids because they lack a triangular face.

In geometry, a prism is a three-dimensional figure consisting of a base and two parallel sides called "prismatic walls" which meet at right angles where they intersect. Thus, a prism has two perpendicular planes of symmetry. Many crystals exhibit this structure and are therefore prismatic. Prisms are important in optics and semiconductors. They can be made by gluing together two identical truncated cubes.

There are several varieties of triangular pyramids. The first is a pyramid with a base and sides that are all the same length. The base of **the regular tetrahedron** should be an equilateral triangle for **the triangular pyramid**. A pyramid has a base and sides of varying lengths. The triangular pyramid's base has **uneven sides**. There are two kinds of triangular pyramids: those with angles between 60 and 120 degrees, called "regular" or "true" triangles; and those with angles greater than 120 degrees, called "irregular" or "assumed" triangles.

The second type of triangular pyramid has three equal sides and an angle between them of 120 degrees. This is also called a "triangle". Although this seems like it would be a simple matter to construct, it can be done only by using geometry. The third type of triangular pyramid has two opposite and equal sides and two opposite and unequal sides. It is not possible to make a true triangular pyramid out of flat boards, but they are sometimes made with curved surfaces. In fact, some pyramids such as the Great Pyramid of Giza were built with curves instead of straight lines.

The fourth type of triangular pyramid has three sides of different lengths and an angle between them of 120 degrees.

A pyramid is a three-dimensional shape with a single base. Any polygon can be used as the base. The remaining faces are triangles. The name of a pyramid is derived from the form of **its base**. There are two kinds of pyramids: those that are equal on all sides and those that have **one side** shorter than the others.

There are two ways to look at a pyramid. You can see it as a flat-topped mountain or as a tall, thin tower. Either way, it's easy to build your own pyramid. Start by choosing a stable platform about half your height. Now get yourself some lumber and construct a solid frame, using wood screws. When that's done, attach it to the platform with metal bolts called lag screws. Finally, cover the whole thing with plaster or mortar.

This is an excellent exercise for building up your confidence if you're feeling scared or unsure of yourself. It's also fun! Once you've built one, you'll want to start stacking more and more blocks until they reach **the desired height**.

As long as you don't go beyond **your comfort zone**, you should have no problems reaching high places. If anything feels too hard or dangerous, then just choose something closer to home to build first.