Eindvlak

Eindvlak is a term in geometry that refers to one of the end faces of certain solids, in particular prisms and cylinders. Each eindvlak is a plane region that forms the boundary at an end of the solid.

For prisms, there are exactly two eindvlakken, which are congruent and parallel to each other; these faces are the bases of the prism. The lateral faces connecting the eindvlakken are parallelograms. The distance between the eindvlakken is called the height of the prism. The volume of a prism is the product of the area of an eindvlak (the base) and the height. In a right prism the lateral edges are perpendicular to the eindvlakken; in oblique prisms they are not perpendicular but still parallel to each other, and the eindvlakken remain parallel.

For cylinders, eindvlak refers to the circular end faces. The two circle-shaped eindvlakken have the same radius and lie in parallel planes; the height of the cylinder is the distance between these end faces. Cross-sections parallel to an eindvlak are congruent and equal to the base shape.

In many texts the term eindvlak is used interchangeably with basisvlak, the base plane, especially when referring to the end faces of prisms and cylinders. The term is part of basic solid geometry and is common in Dutch mathematics education.