# Definition:Cone/Apex

(Redirected from Definition:Apex of Cone)

## Definition

Consider a cone consisting of the set of all straight lines joining the boundary of a plane figure $PQR$ to a point $A$ not in the same plane of $PQR$:

In the above diagram, the point $A$ is known as the apex of the cone.

## Linguistic Note

The plural of apex is apices, which is pronounced ay-pi-seez.

The form apexes can often be seen, but this is technically incorrect.

Compare vertex.

## Comment

Hence the colloquial phrase base over apex as the description of a particularly flamboyant physical tumble.