Cup (US)ĭefinition: A cup is a unit of volume in the imperial and United States customary systems of measurement. It is also used to measure certain non-liquid volumes such as the size of car trunks, backpacks and climbing packs, computer cases, microwaves, refrigerators, and recycling bins, as well as for expressing fuel volumes and prices in most countries around the world. However, due to the mass-volume relationship of water being based on a number of factors that can be cumbersome to control (temperature, pressure, purity, isotopic uniformity), as well as the discovery that the prototype of the kilogram was slightly too large (making the liter equal to 1.000028 dm 3 rather than 1 dm 3), the definition of the liter was reverted to its previous, and current definition.Ĭurrent use: The liter is used to measure many liquid volumes as well as to label containers containing said liquids. History/origin: There was a point from 1901 to 1964 when a liter was defined as the volume of one kilogram of pure water under the conditions of maximum density at atmospheric pressure. One liter is equal to 1 cubic decimeter (dm 3), 1,000 cubic centimeters (cm 3), or 1/1,000 cubic meters (m 3). Definition: A liter (symbol: L) is a unit of volume that is accepted for use with the International System of Units (SI) but is technically not an SI unit.
