 A linear function "f" on a preordered vector space is called positive if "x" ≥ 0 implies "f"("x") ≥ 0.The set of all positive linear forms on a vector space, denoted by formula_89, is a cone equal to the polar of −"C".The order dual of an ordered vector space "X" is the set, denoted by formula_90, defined by formula_91.