Vertex (geometry)

A vertex is a point where two or more sides or edges meet. In some figures, the term also names a distinguished point such as a conic’s apex.

Line segment: A part of a line bounded by two endpoints. Polygon sides are line segments whose endpoints become vertices.
Vertex degree: The number of edges incident to a vertex in a graph. Degree measures how many connections meet at a graph vertex.
Triangle: A polygon with three sides and three vertices. Its three corners provide the simplest polygonal example of vertices.
Endpoint: A point at either end of a line segment, ray, or interval. An endpoint can terminate one segment without being a corner where multiple sides meet.
Polygon: A plane figure bounded by a finite sequence of straight line segments. Its corners are vertices, linking the point concept to a complete figure.
Interior angle: An angle inside a polygon formed by two adjacent sides. The sides meeting at a polygon vertex determine its interior angle.
Tetrahedron: A polyhedron with four triangular faces, six edges, and four vertices. Each of its four vertices is shared by three edges and three faces.
Critical point: A point where a differentiable function has zero derivative or an undefined derivative. A conic’s vertex is not generally defined by the calculus meaning of critical point.
Polyhedron: A three-dimensional solid bounded by polygonal faces. Its edges meet at vertices, extending the idea from plane figures into space.
Convex hull: The smallest convex set containing a given set of points. Extreme input points become vertices of the hull, while interior points do not.

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