The common endpoint of the sides of an angle is called a vertex. For example, triangles have three vertices, while squares have four. These common endpoints are often colloquially called corner points, though this may result in confusing them with angles.
Vertices are a common element of polygons, solid three-dimensional shapes and angles formed by rays or line segments. They are sometimes divided up into ears and mouths, when describing the vertices of irregularly shaped polygons. Ears are vertices which protrude past a certain boundary line, while mouths are vertices that lie inward of the boundary. Ear and mouth vertices make up anthropomorphic polygons.