Mile/hour (mph)
Definition: Mile per hour (symbol: mph) is a unit of speed in the imperial and US customary systems. It expresses the number of statute miles traveled over the period of one hour.
History/origin: The mile per hour has been used as a unit of speed since the adoption of the mile as a unit of distance. It is commonly used in the United States and United Kingdom for speed limits and vehicle speeds.
Current use: The mile per hour is primarily used in the United States, United Kingdom, and a few other countries for measuring speed limits, vehicle speeds, and wind speeds.
Kilometer/hour (kph)
Definition: Kilometer per hour (symbol: km/h or kph) is a unit of speed expressing the number of kilometers traveled in one hour. It is the most common unit of speed in the metric system.
History/origin: The kilometer per hour was introduced as part of the metric system in the late 18th century. It is based on the kilometer, which is 1,000 meters.
Current use: The kilometer per hour is used globally for measuring speed limits, vehicle speeds, and wind speeds. It is the standard unit of speed in most countries around the world.