a major division of a government
a division of an institution or business that provides a specified service or deals with a specified subject
the sales department
the geography department
a major administrative subdivision, e.g. in France
a section of a department store
informal
a distinct sphere, e.g. of activity or thought; an area of responsibility; a speciality
That's not my department
a particular aspect, esp of somebody's physical or mental makeup
rather deficient in the brains department
departmental /deepahtʹmentl/ adj
departmentally /deepahtʹmentəli/ adv
[French département, from Old French departir: see depart]