Vertex

There are multiple uses of the word vertex in mathematics, including uses in graph theory and multiple uses in geometry.

Vertex of a parabola

The vertex of a parabola is the point which, if a vertical line is placed over it, divides the parabola into two equal mirror images.

Vertex of an angle

See angle.

Vertex of a polygon or polyhedron

See polygon.

Note that the plural form of the word "vertex" is the word "vertices;" the singular of "vertices" is "vertex," not "vertice."