What is the difference between company and firm? Do we say a law company? Are they different in the nature of the business? Thanks a lot.
I had always thought that, where both are incorporated entities, firms tend to be professions: law, medicine, accountancy. I see, however, that it also has another definition: A commercial partnership of two or more persons, especially when unincorporated. Well, that gibes somewhat with my image, since law firms and medical firms tend to be partnerships.
A firm can be, amongst other things, a company. See:

can have several meanings: ---------
Law firms and architects' firms are usually partnerships, thus/and they aren't called companies.

But in many contexts, firm and company are both synonymous with business (unit):


3: a business unit or enterprise <the organizational framework within which the Soviet firm operates -- Holland Hunter>