noun
regular polyhedron
A polyhedron whose faces are congruent regular polygons and whose vertices are all alike. Used in geometry.
正多面体は全部で五種類しか存在しない。
There are only five regular polyhedra in total.
多面体 is a general polyhedron, while 正多面体 specifically means a regular polyhedron with congruent regular faces.
Compound of 正 (regular) + 多面体 (polyhedron). The exact historical derivation is uncertain, but the term follows standard mathematical naming conventions.