n. Reciprocal relation; interdependence or interconnection.n. The act of bringing into orderly connection or reciprocal relation.n. In physiology, specifically, the interdependence of organs or functions; the reciprocal relations of organs.n. In geometry, such a relation between two planes that to each intersection of lines in either there corresponds in the other a line of junction between points corresponding to the intersecting lines in the first plane; also, a relation between two spaces such that to every point in either there corresponds a plane in the other, three planes in either intersecting in a point corresponding to the plane of the three points in the other space to which the three intersecting planes correspond; more generally, a relation between figures, propositions, etc., derivable from one another in an n-dimensional space by interchanging points with (n—1) -dimensional flats.n. In statistics, the relation of two or more variable quantities.