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In geometry, a rhombohedron is a three-dimensional figure like a cube, except that its faces are not squares but rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be used to define the rhombohedral lattice system, a honeycomb with rhombohedral cells. In general the ''rhombohedron'' can have three types of rhombic faces in congruent opposite pairs, ''C''''i'' symmetry, order 2. Four points forming non-adjacent vertices of a rhombohedron necessarily form the four vertices of an orthocentric tetrahedron, and all orthocentric tetrahedra can be formed in this way.〔.〕 == Rhombohedral lattice system == The rhombohedral lattice system has rhombohedral cells, with 3 pairs of unique rhombic faces: :120px 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「rhombohedron」の詳細全文を読む スポンサード リンク
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