Roget's Thesaurus of English Words and Phrases by Peter Mark Roget

12. [Double or reciprocal relation.] Correlation — N. reciprocalness

&c adj.†; reciprocity, reciprocation; mutuality, correlation, interdependence, interrelation, connection, link, association; interchange &c 148; exchange, barter. reciprocator, reprocitist. V. reciprocate, alternate; interchange &c 148; exchange; counterchange†. Adj. reciprocal, mutual, commutual†, correlative, reciprocative, interrelated, closely related; alternate; interchangeable; interdependent; international; complemental, complementary. Adv. mutually, mutatis mutandis [Lat.]; vice versa; each other, one another; by turns &c 148; reciprocally &c adj.. Phr. happy in our mutual help [Milton].