Beam: The measurement of a boat at its widest point.
Draft: The depth of yacht under the water measured vertically. An important measure, especially when one navigates shallow waters.
Hull: The part of the boat that stays below the waterline and is built to flow.
Monohull: A yacht with one hull. Although most motor yachts also have one hull, the term typically refers to sailing boats.
Multihull: A yacht with more than one hull, usually with two hulls like a catamaran.
Port: The left side of the boat looking towards the bow. This side is marked by a red navigation light from dusk to dawn.
Starboard: The right side of the boat facing towards the bow. It is marked by a green navigation light.
Windward: The side of the boat that is closer to the wind. On heeling, this will be the high side.
Leeward: The opposite of windward; the side of the boat farthest from the wind. On heeling this will be the low side.