Janus, agglomeration, agglutination, aggregation, ambiguity, ambivalence, articulation, biformity, bifurcation, bond, bracketing, clustering, combination, communication, concatenation, concourse, concurrence, confluence, congeries, conglomeration, conjugation, conjunction, connection, convergence, copulation, coupling, dichotomy, doubleness, doublethink, doubling, dualism, duality, duplexity, duplication, duplicity, equivocality, gathering, halving, hookup, intercommunication, intercourse, interlinking, irony, joinder, joining, jointure, junction, knotting, liaison, linkage, linking, marriage, meeting, merger, merging, polarity, splice, symbiosis, tie, tie-in, tie-up, twinning, two-facedness, twoness, unification, union, yoking