tet·ra·he·dral /ˌtɛtrəˈhidrəl/
  (a.)有四面的,四面體的
  Tet·ra·he·dral a.
  1. Having, or composed of, four sides.
  2. Crystallog. (a) Having the form of the regular tetrahedron. (b) Pertaining or related to a tetrahedron, or to the system of hemihedral forms to which the tetrahedron belongs.
  Tetrahedral angle Geom., a solid angle bounded or inclosed by four plane angles.
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