A sailboat or sailing boat is a boat propelled partly or entirely by sails. The generic term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a smaller vessel (such as a sailboard) varies by region and maritime culture.At present, a great number of sailboat-types may be distinguished. Apart from size, sailboats may be distinguished by a hull configuration (monohull, catamaran, trimaran), keel type (full, fin, wing, centerboard etc.), purpose (sport, racing, cruising), number and configuration of masts, and sail plan. Although sailboat terminology has varied across history, many terms now have specific meanings in the context of modern yachting.The following sub-sections outline the most popular monohull sailing vessels. Additional types of vessels, such as multi-hull, are not discussed in these sub-sections.Today, the most common sailboat is the sloop, which features one mast and two sails: a normal mainsail, and a headsail. This simple configuration is very efficient for sailing towards the wind. The mainsail is attached to the mast and the boom, which is a spar capable of swinging across the boat, depending on the direction of the wind. Depending on the size and design of the headsail it can be called a jib, Genoa, or spinnaker.