Setting the side “law” and “legal” in the phrase law or legal department (See my post of May 24, 2005 for the difference between “law department” and “legal department.“), what is the essence of department? Related terms include “function,” “team,” “office,” “group,” and “unit” – all groups of people with a shared goal. But that definition of a group with shared goals applies not just to a department but to an entire company!
The essence of “department” (See my post of June 13, 2006 on words compared to concepts.) is a small unit of a company, recognized to have a specialized purpose, a fair degree of managerial autonomy, a budget, and something akin to professionalism because its senior members share values, an education, and collegial expectations. A department does not manage profit and loss and it plays second fiddle, as a support function, to client-facing business operations.