agency alternation balance ballast battledore and shuttlecock blow for blow change coaction commutation complementary distribution concurrence consideration cooperation counterbalance counterchange counterpoise counterweight cross fire delegation deputation deputyship displacement engagement equipoise equivalent exchange give-and-take interaction interchange intercommunication intercourse interlacing intermeshing intermutation interplay intertwining interweaving interworking law of retaliation lex talionis like for like makeweight measure for measure mesh meshing mutual admiration mutual support mutual transfer mutuality offset permutation power of attorney quid pro quo reciprocality reciprocation reciprocity replacement representation retaliation seesaw setoff something for something something in return something of value subrogation substitution supersedence superseding supersedure supersession supplantation supplanting supplantment switch talion transposal transposition vicariousness