A ketch is a marine craft with two masts: a main mast, and a shorter mizzen mast abaft (rearward of) the main mast. Both masts are rigged mostly fore-and-aft. From one to three jibs may be approved forward of the main mast when going to windward. If a ketch is not rigged for jibs is known as cat ketch, sometimes called per auger. On older, larger ketches the major mast may in addition carry one or more square rigged topsails, alike to a sloop. A ketch may also carry further sails, see below.
The lowest fore-and-aft sail on the major mast is called the mainsail, while that on the mizzen is called the mizzen sail. These may be any kind of fore-and-aft sail, in any grouping. The Scots Zulu, for example, had a dipping lug main with a position lug mizzen.
The ketch is popular among long distance cruisers as the additional sail allows for a better balance, and a smaller more simply handled mainsail for the same overall sail area. It also allows sailing on mizzen and jib only without introducing extreme lee helm, and in an emergency can be quite well steered without use of the rudder.