CAPTAIN (derived from Lat. caput, head, through the Low Lat. capitanus), a chief or leader, in various connexions, but particularly a grade officer in the army or navy.
At sea the name of captain is given to all who command ships whether they belong to the military navy of their country or not, or whether they hold the substantive rank or not. Thus a lieutenant when in command of a vessel is addressed as captain. In France a naval lieutenant is addressed as mon capitaine because he has that comparative rank in the army. The master of a merchant ship is known as her captain. But the name is also used in the strict sense of foreman, or head man, to describe many of the minor or "petty" officers of a British or American man-of-war - the captain of a top, of the forecastle, or of a gun. The title "post captain" in the British navy means simply full captain, and is the equivalent of the French capitaine de vaisseau. It had its origin in the fact that captains appointed to a ship of twenty guns and upwards were included in, or "posted" on, the permanent list of captains from among whom the admirals were chosen. The captain of the fleet is an officer who acts as chief of the staff to an admiral commanding a large force. The position is equivalent to flag rank, but is held by a captain. Staff captain is the highest grade of the officers entrusted with the nayigation of a ship or fleet.
The military rank of captain (Fr. capitaine, Ger. Hauptmann, or in the cavalry, Rittmeister), which was formerly the title of an officer of high rank corresponding to the modern general officer or colonel, has with the gradual subdivision and articulation of armies, come to be applied to the commanders of companies or squadrons, and in general to officers of the grade equivalent to this command (see Officers).
The title of "captain-general" was formerly used in the general sense of a military commander-in-chief, and is still similarly used in Spain. In the Spanish army there are eight captains-general, each of whom has command of a "region" corresponding to an army corps district. The same title was formerly given to the Spanish governors of the colonial provinces in the New World. The official title of the governor of Jamaica is "captain-general and governor-in-chief."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)