vertex

noun pl. vertexes or vertices

1. the highest point; summit; apex, as the top point of the sun, moon, etc. above the horizon
2. Anat., Zool. the top or crown of the head
3. Geom.
   1. the point of intersection of the two sides of an angle
   2. a corner point of a triangle, square, cube, parallelepiped, or other geometric figure bounded by lines, planes, or lines and planes
4. Optics the point at the center of a lens at which the axis of symmetry intersects the curve of the lens