Deck
A deck refers to one of several levels of a vessel or starship or similar vessel, comparable to floors of a building. The deck itself was typically made of deck plating. ()

An order to "hit the deck" was an Earth nautical term meaning to drop to deck plate. ()

Aboard Earth starships in the 21st and 22nd centuries, decks were named alphabetically; A-deck would be on top, B-deck right below it, etc. This naming scheme was used as early as 2069, aboard the . ()

By the 23rd century, Federation starships had adopted a system where the upper level was referred to as deck 1. Deck numbers then increased for each deck below, the lowest level having the highest number. For example, the  's lowest deck was deck 15. ()

However, aboard the refit  , the decks were ordered alphabetically again rather than numerically. The bridge was located on Deck A (as indicated by signage on the turbolift doors). Following an attack by Khan Noonien Singh in 2285, the turbolifts aboard the Enterprise were rendered inoperative below C-Deck. ()

Deck charts 
Federation starship decks
California-class decks
Constitution-class decks
Crossfield-class decks
Defiant-class decks
Excelsior-class decks
Galaxy-class decks
Intrepid-class decks
Nova-class decks
Oberth-class decks
Sovereign-class decks
Walker-class decks
United Earth Starfleet
NX-class decks
Vulcan starship decks
D'kyr-type decks

External link 
 
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Spacecraft parts