A vertex is a point where two or more lines, edges, or sides meet to form a corner or angle. On a triangle, each of the three corners is a vertex. On a cube, each of the eight corners where three edges come together is a vertex. The plural of vertex is vertices (pronounced VER-tih-seez).

You encounter vertices constantly in geometry class. When drawing shapes, you often start by marking the vertices with dots, then connecting them with straight lines. A square has four vertices, a pentagon has five, and a soccer ball's pattern contains dozens of vertices where the hexagons and pentagons meet.

In three-dimensional shapes, vertices are particularly important: they help define the shape's structure. Think of building a tent: the vertices are where the poles meet and hold the whole structure together.

Mathematicians use vertices to study graphs and networks too. On a family tree, each person might be represented by a vertex, with lines showing relationships. In computer graphics, vertices define the corners of every three-dimensional object you see in video games, from the simplest cube to the most complex character model.