# Definition:Prism

## Definition

In the words of Euclid:

A prism is a solid figure contained by planes of which, namely those which are opposite, are equal, similar and parallel, while the rest are parallelograms.

## Faces of Prism

### Base

The bases of a prism are the two parallel polygons which form the faces at either end of the prism.

In the above diagram, the faces $ABCDE$ and $FGHIJ$ are the bases of the prism.

### Lateral Face

The lateral faces of a prism are the parallelogramic faces which join the bases.

In the above diagram, the faces $ABGF, BCHG, CDIH, DEJI$ and $EAFJ$ are the lateral faces of the prism.

### Opposite

Let $P$ be a prism whose bases are $P_1$ and $P_2$.

The opposite face of the base $P_1$ is the base $P_2$.

In the above example, the base $ABCDE$ is opposite $FGHIJ$.

## Height

The height of a prism is the length of the perpendicular between the bases of the prism.

In the above diagram, the distance $h$ is the height of the prism $AJ$.