Mile per hour (mph)
The mile per hour, symbolized as mph, is an imperial unit that expresses speed in miles traveled per hour. It originated in England, where miles were the standard measure of distance, and gained prominence with the advent of road travel and railways. One mph equals 1.60934 kilometers per hour. The unit remains widely used in the United States, the UK, and a few other countries for road speed limits, automotive specifications, and aviation. Despite global metric adoption, mph persists in daily life and transportation, reflecting historical continuity and practical familiarity in imperial-system countries.
Knot (kn)
The knot (kn) is a unit of speed based on nautical miles per hour, widely used in both maritime and aviation navigation. The term comes from an early method where sailors used a rope, known as a log line, with evenly spaced knots to gauge a ship’s speed. By counting the number of knots that passed overboard during a set period, they could estimate how fast the vessel was moving. One knot is defined as one nautical mile per hour, equivalent to roughly 1.852 kilometers per hour. Today, the knot is universally adopted for sea and air navigation, providing a consistent and reliable standard for measuring speed in global transportation.