A kilo, short for kilogram, is a unit of mass in the metric system. It is defined as being equal to 1,000 grams. The kilogram is the base unit of mass in the International System of Units (SI) and is widely used around the world for measuring weight in various contexts, such as food, science, and industry. The kilogram was originally based on a physical object, a platinum-iridium cylinder known as the International Prototype of the Kilogram. In 2019, the definition was updated to be based on fundamental constants of nature, specifically the Planck constant, ensuring greater accuracy and stability in measurements.