Meter (m)
Definition: The meter (symbol: m) is the base unit of length in the International System of Units (SI). It is defined by taking the fixed numerical value of the speed of light in vacuum c to be 299,792,458 when expressed in the unit m/s.
History/origin: The meter was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1983, the meter was redefined in terms of the speed of light.
Current use: The meter is used globally in science, engineering, and commerce. It is the standard unit of length in most countries around the world.
Yard (yd)
Definition: A yard (symbol: yd) is a unit of length in the imperial and US customary systems of measurement. It is defined as exactly 0.9144 meters. The yard is subdivided into 3 feet or 36 inches.
History/origin: The yard has been used as a unit of measurement since the 12th century. It was originally defined as the distance from the tip of King Henry I's nose to the end of his outstretched thumb. In 1959, the international yard was defined as exactly 0.9144 meters.
Current use: The yard is primarily used in the United States and United Kingdom for measuring distances, especially in sports like American football and golf. It is also used in various other applications.