The word "党同伐异" is formed by combining four characters: "党" meaning to form a faction or align with, "同" meaning those who are the same or agree, "伐" meaning to attack or oppose, and "异" meaning those who are different or dissent. It structurally pairs "党同" (siding with the like-minded) with "伐异" (attacking the dissimilar) to create a compound that describes the act of uniting with one's own group while antagonizing others.