The knot (pronounced 'not') is a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.151 mph. The abbreviation \(kn\) is preferred by the International Hydrographic Organization (IHO), which includes every major sea-faring nation; however, the abbreviations kt (singular) and kts (plural) are also widely used. However, use of the abbreviation kt for knot conflicts with the SI symbol for kilotonne. The knot is a non-SI unit accepted for use with the International System of Units (SI). Worldwide, the knot is used in meteorology, and in maritime and air navigation - for example, a vessel travelling at 1 knot along a meridian travels one minute of geographic latitude in one hour. Etymologically, the term knot derives from counting the number of knots in the line that unspooled from the reel of a chip log in a specific time.