A knot (symbol kt or kn) is the standard unit of speed used in maritime and aviation contexts, defined as one nautical mile per hour (≈1.852 km/h or 1.15078 mph). It measures how quickly a vessel or aircraft travels across the water or through the air, providing a universally understood reference for navigation, weather forecasting, and fuel planning. Because a nautical mile is based on the Earth's geometry, knots directly relate distance to latitude and longitude, making them essential for accurate chart plotting, route optimization, and safety calculations in both practical sailing and scientific research such as oceanography and aerodynamics.