Hypertext Webster Gateway: "tetrahedron"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Tetrahedron \Tet`ra*he"dron\, n. [Tetra- + Gr. ? seat, base, fr.
? to sit.] (Geom.)
A solid figure inclosed or bounded by four triangles.
Note: In crystallography, the regular tetrahedron is regarded
as the hemihedral form of the regular octahedron.
{Regular tetrahedron} (Geom.), a solid bounded by four equal
equilateral triangles; one of the five regular solids.
From WordNet (r) 1.7 (wn)
tetrahedron
n : any polyhedron having four plane faces
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