A polyhedron that has a base and three or more triangular faces that meet at a point

above the base (the apex).

above the base (the apex).

A pyramid is a polyhedron that has a base, which can be any polygon, and three or more triangular faces that meet at a point called the apex. These triangular sides are sometimes called the lateral faces to distinguish them from the base.

The base can be any polygon, but is most often a square. In the figure above click on the 'more/less' buttons to change the number of base sides. Notice that as the number of sides gets large, the pyramid begins to look a lot like a cone. In fact a pyramid and cone have a lot in common - for example the volume of the two are calculated the same way (See Volume of a Pyramid).

The base is usually a regular polygon, but it need not be. In the figure above, click off the "regular base" checkbox, then rotate the pyramid by dragging it to see the effect of this.

- If the apex is directly over the center of a regular base as it is above, it is called a
**right pyramid**. - If the apex is not over the center of the base, it is called an
**oblique pyramid**, and the faces are not congruent.

See Oblique pyramid definition for more on this.

- Definition and properties of a pyramid
- Oblique and right pyramids
- Volume of a pyramid
- Surface area of a pyramid

- Cylinder - definition and properties
- Oblique cylinders
- Volume of a cylinder
- Volume of a partially filledcylinder
- Surface area of a cylinder

- Definition of a cone
- Oblique and Right Cones
- Volume of a cone
- Surface area of a cone
- Derivation of the cone area formula
- Slant height of a cone

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