The knot (kn) is a unit of speed equal to one nautical mile per hour. It is not an SI unit but is widely used in maritime and aviation contexts. One knot is defined as 1.852 kilometers per hour (km/h) or 1.15078 miles per hour (mph).
The term "knot" originated in the 16th century when sailors used a log line with knots tied at regular intervals to measure a ship's speed. The number of knots that passed through a sailor's hands in a specific time indicated speed in nautical miles.
Knot is predominantly used in maritime and aviation environments to measure the speed of vessels and aircraft. It is essential for navigation, allowing sailors and pilots to gauge distances over water and air accurately.