第ㄉㄧˋdì三ㄙㄢsān者ㄓㄜˇzhě

當事雙方以外的人或團體。如甲乙兩方訂定契約，而須負連代保證責任的丙方，即為第三者。似局外人
夫妻外遇的對象或情侶移情的對象。如：「這對青梅竹馬，因 第三者的介入而告分手了。」

英sb who is romantically involved with sb already in a committed relationship, the other woman, the other man, third person, third party (in dispute), disinterested party, number three in a list

法tiers, tierce personne, amant, maîtresse