A diagonal can refer to a line joining two nonconsecutive vertices of a polygon or polyhedron, or in informal contexts any upward or downward sloping line. The word "diagonal" derives from the Greek διαγώνιος (diagonios), from dia- ("through", "across") and gonia ("angle", related to gony "knee"); it was used by both Strabo and Euclid to refer to a line connecting two vertices of a rhombus or cuboid,, and later adopted into Latin as diagonus ("slanti… (More on Diagonal)