perpendicularity
  垂直,直立
  Per·pen·dic·u·lar·i·ty n.  The quality or state of being perpendicular.
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  perpendicularity
       n 1: the relation of opposition between things at right angles
            [syn: orthogonality, orthogonal opposition]
       2: the quality of being at right angles to a given line or
          plane (especially the plane of the horizon)