What term is used to indicate the speed of a ship?

The term used to indicate the speed of a ship is "knots." This unit of measurement specifically denotes nautical miles per hour and is widely used in maritime contexts. One knot is equal to one nautical mile per hour, which is about 1.15 statute miles per hour. Using knots allows for a more accurate representation of distance traveled over water since nautical miles are based on the circumference of the Earth, which is more relevant in navigation than standard miles.

Maritime navigation involves the use of charts and navigation systems that are based on the earth's curvature, making knots a preferred unit for sailors and navigators. Other options such as miles per hour, speed units, or maritime speed do not capture this nautical aspect, making "knots" the correct and most appropriate term for speed at sea.