A solid figure with five plane faces.
- ‘You can also have an Egyptian pentahedron square-base pyramid.’
- ‘Whereas the tetrahedron is composed of four triangles, the pyramid (or pentahedron), which looks a lot like it, is composed of four triangles and a square - the base.’
- ‘Then the pyramids are cut by silhouettes into a set of pentahedrons, which together constitute the centripetal pentahedron model of the visual hull.’
Late 18th century: from penta- ‘five’+ -hedron, on the pattern of words such as polyhedron.
We take a look at several popular, though confusing, punctuation marks.