The act or process of centralizing, or the state of being centralized; the act or process of combining or reducing several parts into a whole
An isomorphism from a projective space to the dual of a projective space, often to the dual of itself.
A reciprocal, parallel or complementary relationship between two or more comparable objects.
One of the several measures of the linear statistical relationship between two random variables, indicating both the strength and direction of the relationship.