(n.) The act of retaliating, or of returning like for like; retribution; now, specifically, the return of evil for evil; e.g., an eye for an eye, a tooth for a tooth.

alternation amends atonement avengement avenging balancing battledore and shuttlecock blood feud blow for blow commutation compensation cooperation correction counteraction counterbalancing counterblow counterchange cross fire discipline exchange expiation feud getting even give-and-take indemnification indemnity interchange intermutation interplay lex talionis measure for measure mutual admiration mutual support mutual transfer mutuality offsetting permutation punishment quid pro quo reciprocality reciprocation reciprocity recompense rectification redress reparation repayment reprisal requital restitution retribution revanche revanchism revenge satisfaction something for something substitution sweet revenge tit for tat transposal transposition vendetta vengeance