SI Units
The International System of Units (SI), the modern metric system used globally as the standard language of science and measurement.
SI unit
Dimensionless
In depth
Maintained by the BIPM, the SI system consists of 7 base units (meter, kilogram, second, ampere, kelvin, mole, candela) from which all derived units are formed. In 2019, the SI was re-defined entirely in terms of fixed fundamental physical constants.
Examples in the real world
Expressing energy in Joules (kg·m²/s²) or frequency in Hertz (s⁻¹).