A vertex is a corner. More than one vertex are called vertices. A vertex is a point where two or more lines, curves, rays, or sides meet, and is often represented by letters such as , , and .
For example, the vertex of an angle is the point where the two edges of the angle intersect, and a vertex of a cube is simply one of its corners—of which there are 8.
The concept of vertex applies to both two-dimensional and three-dimensional geometrical objects. For example, a tetrahedron has 4 vertices, and a pentagon has 5 vertices.