1. (用于公司名称中)
Co. is used as an abbreviation for (缩略 =) company when it is part of the name of an organization.

2. (用于郡名之前，尤指爱尔兰的郡)
Co. is used as a written abbreviation for(书面缩略 =)county before the names of some counties, especially in Ireland.

3. (用于人名之后)及其一伙，以及其他成员
You use and co. after someone's name to mean the group of people associated with that person.