Icosahedron

• 20 triangular faces.
• 30 edges.
• 12 vertices.

5 faces (and edges) meet at every vertex.

So the dual polyhedron is the dodecahedron.

I`co*sa*he"dron (?), n. [Gr. ; twenty + seat, base, fr. to sit.] Geom.

A solid bounded by twenty sides or faces.

Regular icosahedron, one of the five regular polyhedrons, bounded by twenty equilateral triangles. Five triangles meet to form each solid angle of the polyhedron.

© Webster 1913.