enemy n. 敌人，敌军 adj. 敌人的，敌方的
例句：After several fails the enemy was forced to retreat.
几经失败之后，敌军被迫后撤。

rival n. 竞争者 对手 v. 竞争，对抗 ，相匹敌
例句：After the national selection, the party leader has been supplanted by his rival.
全民选举之后，那位政党领导已被他的对手取而代之了。

rivalry n. 竞争，竞赛，敌对，敌对状态
例句：Rivalry among business firms in different countries grew More intense.
不同国家的公司之间的竞争趋于激烈。

adversary n. 敌手，对手
例句：It is stupid to overestimate the strategic insight of your adversary as it is dangerous to underrate it.
过高估计你的对手的战略远见是愚蠢的，估计过低也是危险的。

adverse adj. 不利的，敌对的，相反的
Adverse environment forced the company to abort the development plans.
不利的环境使得公司中止了发展计划。

opponent adj. 对立的．对抗的 n. 对手，反对者
例句：I tried to comfort Phoebe after she was defeated by her opponent in business.
菲比被她生意上的对手击败后，我尽力安慰她。

oppose vt. 反对，使对立，使对抗，抗争 vi. 反对
例句：I oppose砌chard to use the office computer for the private affairs.
我反对理查德为私事使用办公室电脑。

ally v. 结盟，同盟 n. 同盟国，支持者
例句：Britain was an ally of America in the World War I.
英国在第一次世界大战中是美国的同盟国。

alloy n. 合金 vt. 使成合金，减低成色
例句：Aluminium alloy could be as strong as steel.
铝合金可以和钢强度一样大。