1. Opponent, competitor, rival refer to persons engaged in a contest. Opponent is the most impersonal, meaning merely one who opposes; perhaps one who continually blocks and frustrates or one who happens to be on the opposite side in a temporary contest: an opponent in a debate. Competitor emphasizes the action in striving against another, or others, for a definite, common goal: competitors in business. Rival has both personal and emotional connotations; it emphasizes the idea that (usually) two persons are struggling to attain the same object: rivals for an office.

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