quantity in a conventionally chosen subset of a given system of quantities, where no subset quantity can be expressed in terms of the others
NOTE 1 The subset mentioned in the definition is termed the “set of base quantities”.
EXAMPLE The set of base quantities in the International System of Quantities (ISQ) is given in 1.6.
NOTE 2 Base quantities are referred to as being mutually independent since a base quantity cannot be expressed as a product of powers of the other base quantities.
NOTE 3 'Number of entities' can be regarded as a base quantity in any system of quantities.