ESP, alternation, answer, battledore and shuttlecock, coact, coaction, commerce, communication, communion, commutation, complementary distribution, concurrence, congress, connection, contact, conversation, converse, cooperate, cooperation, correspondence, counterchange, cross fire, dealing, dealings, dovetail, engage, engagement, exchange, give-and-take, information, interact, interaction, interchange, intercommunication, intercommunion, intercourse, interlace, interlacing, intermesh, intermeshing, intermutation, intertwine, intertwining, interweave, interweaving, interwork, interworking, lex talionis, linguistic intercourse, measure for measure, mesh, meshing, message, mortise, mutual admiration, mutual support, mutual transfer, mutuality, permutation, quid pro quo, reciprocality, reciprocation, reciprocity, reply, response, retaliation, seesaw, social intercourse, something for something, speaking, speech, speech circuit, speech situation, talking, telepathy, tit for tat, touch, traffic, transposal, transposition, truck, two-way communication