company 多指生产或销售产品的公司、商号，也可指经办服务性项目的公司。
corporation 多指一个人拥有或多人联办的大公司，也指在其它地区或国家拥有分公司的公司。
firm 含义广泛，可指公司、商行或商号。规模可大可小，经营、管理的人员可多可少。
参考例句
1. He reshuffled the cabinet to firm his government. 他改组内阁以强化其政府。
2. We have an inquiry for the goods received from the firm. 我公司已收到，该公司关于这类商品之询盘。
3. We are a generalist search firm instead of a specialist one. 我们代替一专家那个是一个多面手搜索公司。
英英解释
n.
1. the members of a business organization that owns or operates one or more establishments
2. become taut or tauter
3. make taut or tauter adj.
1. marked by firm determination or resolution; not shakable
2. not soft or yielding to pressure
3. strong and sure
4. not subject to revision or change
5. (of especially a person's physical features) not shaking or trembling
6. not liable to fluctuate or especially to fall
7. securely established
8. possessing the tone and resiliency of healthy tissue
9. pleasingly firm and fresh and making a crunching noise when chewed
10. securely fixed in place
11. unwavering in devotion to friend or vow or cause adv.
1. with resolute determination
