A yawl is a type of boat. The term has several meanings. It can apply to the rig (or sailplan), to the hull type or to the use which the vessel is put.
As a rig, a yawl is a two masted, fore and aft rigged sailing vessel with the mizzen mast positioned abaft (behind) the rudder stock, or in some instances, very close to the rudder stock. This is different from a ketch, where the mizzen mast is forward of the rudder stock. The sail area of the mizzen on a yawl is consequentially proportionately smaller than the same sail on a ketch.
As a hull type, yawl may refer to many types of open, clinker-built, double-ended, traditional working craft that operated from the beaches of the British Isles. These boats are considered to be linked to the Viking or Nordic design tradition. Most of these types are now extinct, but they include the Norfolk and Sussex Beach Yawls (called "yols" by the men who crewed them), which were probably the fastest-sailing open boats ever built.
A yawl is also a type of ship's boat. The definition, size, number of oars and sailing rig varied over time. This was one of the normal working boats carried by a ship in the age of sail.
In local usage, the term yawl was sometimes applied to working craft which did not fit any of the definitions given above. An example of this is the Whitstable yawl, a decked gaff-cutter-rigged fishing smack that dredged for oysters.
The etymology of "yawl" is obscure - especially considering the different meanings of the word.