‘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.’
‘You can also have an Egyptian pentahedron square-base pyramid.’
‘Then the pyramids are cut by silhouettes into a set of pentahedrons, which together constitute the centripetal pentahedron model of the visual hull.’
Origin
Late 18th century from penta-‘five’ + -hedron, on the pattern of words such as polyhedron.
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