Vertex in an angle: The point in which the sides of the angle meet. That is, the common endopoint of the two rays.
The point about which an angle is measured is called the angle´s vertex, and the angle
associated with a given vertex is called the vertex angle.
Vertex in a polygon: The vertices of a polygon are the points where its sides intersect.
Vertex of a cone or a pyramid: The vertex of a cone or a pyramid is the point opposite to the base. That is, the point placed (vertically) above the base.
Vertices of a polyhedron: A vertex od a polyhedron is a point at which three or more edges intersect.
Diagonals in a polygon: The diagonal of a polygon is a line segment that joins two non-consecutive vertices.
The number of diferent diagonals is given by the formula:
where n is the number of sides or vertices.