The horizontal platforms in ships corresponding to floors in houses. Starting from the bottom, the decks in an average large ship are the orlop, lower (though the two are now sometimes combined in a single deck known as the lower), main, upper, shelter, bridge, and boat. These, however, may vary considerably from ship to ship according to its function. Smaller ships, of course, have fewer decks; larger ones have more. The ocean liner Queen Elizabeth II, for instance, has thirteen. In some types of ships, these decks have other names: in large liners, for example, the shelter deck is frequently known as the promenade deck, and other names have been coined to denote different decks according to their main purpose, such as hurricane deck, cabin deck, etc. In the days of the sailing navies, the upper deck was often known as the spar deck, and the main deck as a gun-deck. But see also decker for warships with more than one gun-deck.
Properly speaking, a deck must extend the full length of the ship, but in cases where it does not extend the full length, the word is still used, if improperly, to describe the built-up portions forward and aft of a ship, the fore portion being known as the forecastle deck and the after portion as the poop deck. That portion of the upper deck which lies between forecastle and poop is often known in merchant ships as the well deck, and in many other types of ship as the waist.
The origin of the term is obscure but it probably comes from the Old Dutch dec, a covering, cloak, or horse-cloth, although in its nautical meaning the word was in use in England at least a century and a half earlier than in Holland.
Subjects: Maritime History.