SI base unit referenced to the values of the fundamental constants, namely the Planck constant ("h"), the electron charge ("e"), the Boltzmann constant ("k"), and the Avogadro constant ("N"). This approach was approved in 2018, only after measurements of these constants were achieved with sufficient accuracy. SI base unit The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units can be derived. The SI base units and their physical quantities are the meter for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin
Atomic mass unit names for the same unit of measure. As with other unit names such as watt and newton, "dalton" is not capitalized in English, but its symbol, Da, is capitalized. With the introduction of the name "dalton", there has been a gradual change towards using that name in preference to the name, "unified atomic mass unit": The former definition of the mole, an SI base unit, was accepted by the CGPM in 1971 as: However, the first part of this definition was changed in 2018 to: One consequence of this change is that the current defined relationship between the mass of