A diagonal is a line segment joining two non-adjacent vertices of a polygon or polyhedron.
Diagonal may also refer to: Diagonal brace, a beam used to brace a rectangular structure (such as scaffolding) to withstand strong forces pushing into it Diagonal pliers, wire-cutting pliers whose cutting edges intersect the joint rivet "on a diagonal" Diagonal lashing, a type of lashing used to bind spars or poles together so that the lashings cross over the poles at an angle Diagonal system of control, the method referees and assistant referees use to position themselves in one of the four quadrants of an association football pitch Main diagonal, the entries of a matrix whose row and column indices are the same Diagonal matrix, a matrix whose entries off the main diagonal are all zero The natural injection of a set into its Cartesian square, or the image thereof Avinguda Diagonal, a street in Barcelona Diagonal (newspaper), a Spanish newspaper
See also Diagon (disambiguation)