two-decker
{{short description|Type of warship}}
{{About|the type of warship|the bus type|Double-decker bus|other uses|Double decker (disambiguation){{!}}Double decker}}
File:The Moonlight Battle- the Battle off Cape St Vincent, 16 January 1780 RMG BHC0430.jpg by Dominic Serres, with a British two-decker in the foreground.]]
A two-decker is a sail warship which carried her guns on two fully armed decks.{{Cite book |last1=Anderson |first1=Romola |url=https://books.google.com/books?id=Re-7AQAAQBAJ&dq=Two-decker+ship&pg=PA107-IA19 |title=A Short History of the Sailing Ship |last2=Anderson |first2=R. C. |date=2012-06-11 |publisher=Courier Corporation |isbn=978-0-486-14952-3 |language=en}} Usually additional guns were carried on the upper works (forecastle and quarterdeck), but this was not a continuous battery and thus not counted as a full gun deck.
Two-deckers ranged all the way from the small 40-gun Fifth rate up to 80- or even 90-gun ships of the line, with the third-rate of seventy-four guns, or "seventy-four", being the archetype.