What is a Common Vertex? Definition and Examples

What is a common vertex? A common vertex is a vertex that is shared by two or more angles.

Two examples showing what the common vertex is

In the figure below, we see 2 angles named a and b. The common vertex for these two angles is the red dot that you see.

In the figure below, we see 4 angles named 1, 2, 3, 4. The common vertex for these four angles is the red dot that you see.