Kilogram (kg)
Definition: The kilogram (symbol: kg) is the base unit of mass in the International System of Units (SI). It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10⁻³⁴ when expressed in the unit J·s, which is equal to kg·m²·s⁻¹.
History/origin: The kilogram was originally defined in 1795 as the mass of one liter of water. In 1889, the International Prototype of the Kilogram (IPK) was created. In 2019, the kilogram was redefined in terms of fundamental physical constants.
Current use: The kilogram is used globally in science, engineering, and commerce. It is the standard unit of mass in most countries around the world.
Stone (st)
Definition: A stone (symbol: st) is a unit of mass in the imperial and US customary systems of measurement. It is defined as exactly 14 pounds or 6.35029 kilograms. The stone is commonly used in the UK and Ireland for measuring body weight.
History/origin: The stone has been used as a unit of measurement since ancient times. It was originally defined as the weight of a specific number of seeds or grains. The modern stone was standardized in 1959 as exactly 14 pounds.
Current use: The stone is primarily used in the United Kingdom and Ireland for measuring body weight. It is also used in various other applications, such as measuring the weight of animals and produce.