Definition:Polygon/Vertex
Jump to navigation
Jump to search
Definition
A corner of a polygon is known as a vertex.
Thus, in the polygon above, the vertices are $A, B, C, D$ and $E$.
Also defined as
Euclid, in The Elements, uses the term vertex to mean the corner of a polygon furthest up the page from the base.
In the words of Euclid:
- The height of any figure is the perpendicular drawn from the vertex to the base.
(The Elements: Book $\text{VI}$: Definition $4$)
Also see
Note
The vertices and the sizes of the internal angles of those vertices are frequently referred to by the same letter.
Thus the angle of vertex $A$ is called angle $A$ and denoted $\angle A$.
This is considered by some to be an abuse of notation but its convenience outweighs its disadvantages.
Linguistic Note
The plural of vertex is vertices.
The word vertex is Latin for peak, from which the irregular plural form.
Sources
- 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): Entry: vertex: 1a.