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 introduced as the standard. In 2019, the definition was changed to be based on fundamental constants of nature.
Current use: The kilogram is used globally in science, engineering, commerce, and everyday life. It is the standard unit for measuring body weight, food, and goods in most countries.
Pound (lbs)
Definition: The pound (symbol: lb or lbs) is a unit of mass used in the imperial and US customary systems. It is defined as exactly 0.45359237 kilograms. The pound is subdivided into 16 ounces.
History/origin: The pound has been used as a unit of weight since ancient times. The modern avoirdupois pound was standardized in 1959 as exactly 0.45359237 kilograms.
Current use: The pound is primarily used in the United States, United Kingdom, and Canada. It is commonly used for measuring body weight, food, and various goods.