Definitions
1.nounThe dual of a relation.
2.nounA corresponding relationship.
3.nounA reciprocal, parallel or complementary relationship between two or more comparable objects.
4.nounOne of the several measures of the linear statistical relationship between two random variables, indicating both the strength and direction of the relationship.
5.nounAn isomorphism from a projective space to the dual of a projective space, often to the dual of itself.