Physical quantities and SI units
Physical quantities have a numerical value (a number) and a unit of measurement (e.g. two kilograms, one metre, ten newtons).
In "2 kilograms of bananas", "2" is the numerical value and "kilograms" is the unit.
A unit of measurement is a specific magnitude of a physical quantity that has been adopted by convention.
Kilogram, degree Celsius and centimetre are different units.
The International System of Units, abbreviated as SI (in French), defines the set of units of measurement and their symbols that are most widely used by scientists.
The metre is the SI unit for distance. The kelvin is the SI unit for temperature.