A knot is a speed of one nautical mile (6,076 feet or 1852 meters) per hour. In the days of sail, speed was measured by tossing overboard a log which was secured by a line. Knots were tied into the line at intervals of approximately six feet. The number of knots measured was then compared against time required to travel the distance of 1000 knots in the line.
- U.S. Department of Transportation Maritime Administration