Fort
Fort , noun
[French, from fort strong, Latin fortis; perh. akin to Sanskrit darh to fix, make firm, and to English firm Compare Forte, Force, Fortalice, Comfort, Effort.]
(Military) A strong or fortified place; usually, a small fortified place, occupied only by troops, surrounded with a ditch, rampart, and parapet, or with palisades, stockades, or other means of defense; a fortification.
Detached works, depending solely on their own strength, belong to the class of works termed forts.