tetrahedron

== English == === Alternative forms === tetraedrum (obsolete) === Etymology === From Ancient Greek τετράεδρον (tetráedron, “triangle-based pyramid”), from τετράεδρος (tetráedros), from τετράς (tetrás, “four”) + ἕδρα (hédra, “seat”). By surface analysis, tetra- +‎ -hedron. === Pronunciation === enPR: tĕtrəhē'drən, IPA(key): /ˌtɛtɹəˈhiːdɹən/ Rhymes: -iːdɹən === Noun === tetrahedron (plural tetrahedra or tetrahedrons) (geometry) A polyhedron with four faces; the regular tetrahedron, the faces of which are equal equilateral triangles, is one of the Platonic solids. ==== Derived terms ==== ==== Translations ====