Vĕr'tex, n.

n.; Eng. pl. VĒR'TEX-ES; Lat. pl. VĒR'TI-CĒS. [Lat., properly that which turns or revolves about itself, from vertere, to turn, Fr. & Pr. vertere, O. Fr. vertir, Sp., Pg., & It. vertice].

1. A turning-point; principal or highest point; top; summit; crown; hence, specifically, (a.) The crown of the head. (b.) The zenith, or point of the heavens directly overhead.
2. (Math.) The point in any figure opposite to, and furthest from, the base; the terminating point of some particular line or lines in a figure or curve; the top or point opposite the base.

☞— The principal vertex of a conic section is, in the parabola, the vertex of the axis of the curve; in the ellipse, the left-hand vertex of the transverse axis; in the hyperbola, the right-hand vertex of the transverse axis. Math. Dict. Vertex of a curve, the point in which the axis of the curve intersects it.—Vertex of an angle, the point in which the sides of the angle meet.—Vertex of solid, or surface of revolution, the point in which the axis pierces the surface.