a. ‘Separate allotment; province or business assigned to a particular person’ (Johnson); hence in wider application: A separate division or part of a complex whole or organized system, esp. of activities or studies; a branch, province. Frequently in trivial use. [Johnson, 1755, calls it ‘a French term’.]

b. spec. Any one of the separate divisions or branches of state or municipal administration.In the U.S. the word is used in the titles of the great branches of administration, i.e. (in 1988), the Departments (Depts.) of State (originally Foreign Affairs), Treasury, Defense, Justice, Interior, Agriculture, Commerce, Labor, Health and Human Services, Housing and Urban Development, Transportation, Energy, and Education.In Great Britain, the great departments of State were not so named titularly until the mid-20th cent., when a number of new departments were created under that name during the administrative reorganizations of the 1960s and 1970s (alongside others which retained the title Ministry or Office); e.g. (in 1988) the Departments of Education and Science, Employment, Energy, the Environment, Health and Social Security, Trade and Industry, and Transport. The word is also used in naming subdivisions or branches of these, e.g. the Prisons Dept. of the Home Office, and for certain other branches of administration; also in the Departments of a local government authority, as the Highways Department.

c. department of state: (a) = sense 3b; (b) U.S. (with capital initials) the federal government department for foreign affairs; = State Department n. at state n. Compounds 3a.

a. One of the districts into which France is divided for administrative purposes, and which were substituted for the old provinces in 1790. Also applied to administrative divisions in some other countries. Frequently in French form.

b. A part, portion, section, region. rare.