From The Collaborative International Dictionary of English v.0.48:
Department \De*part"ment\, n. [F. d['e]partement, fr.
d['e]partir. See Depart, v. i.]
1. Act of departing; departure. [Obs.]
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Sudden departments from one extreme to another.
--Wotton.
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2. A part, portion, or subdivision.
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3. A distinct course of life, action, study, or the like;
appointed sphere or walk; province.
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Superior to Pope in Pope's own peculiar department
of literature. --Macaulay.
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4. Subdivision of business or official duty; especially, one
of the principal divisions of executive government; as,
the treasury department; the war department; also, in a
university, one of the divisions of instruction; as, the
medical department; the department of physics.
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5. A territorial division; a district; esp., in France, one
of the districts composed of several arrondissements into
which the country is divided for governmental purposes;
as, the Department of the Loire.
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6. A military subdivision of a country; as, the Department of
the Potomac.
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