polyhedron

noun

Etymology: From New Latin polyedron, from Ancient Greek πολύεδρος (polúedros, “having many seats”), from πολυ- (polu-, “many”) + ἕδρα (hédra, “seat”); compare French polyèdre. By surface analysis, poly- + -hedron.

1. A solid figure with many flat faces and straight edges.

   “Of the convex polyhedra with regular faces, the only ones that have tetrahedral, octahedral, or icosahedral symmetry are the Platonic and Archimedean solids.”

2. A polyscope, or multiplying glass.
3. A stage in the growth of Hydrodictyon, when the resting spore breaks up into several megazoospores that put out horn-like appendages; these polyhedra break up into zoospores.