tet·ra·he·dron /ˌtɛtrəˈhidrən/
四面體
tetrahedron
四面體
Tet·ra·he·dron n. 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.
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tetrahedron
n : any polyhedron having four plane faces
[also: tetrahedra (pl)]