Definition:Prism/Opposite

Definition

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 $FGHIJ$.

Also known as

The opposite face can also be referred to as the opposite plane.

Historical Note

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.

(The Elements: Book $\text{XI}$: Definition $13$)