Mainsail

The mainsail is the triangular sail on a sailing boat that is attached to both the mast and the boom (Sailing). The mainsail in conjunction with other sails provides the propulsion for sailing boat designs such as the sloop. The mainsail's lift and power can be adjusted by changing its tension and its angle relative to the wind.

The mainsail's power is often enhanced by that of a jib which helps to produce laminar flow over the mainsail. In downwind conditions (with the wind behind the boat) a spinnaker is also sometimes used.