– Mass is the quantity of matter in a body. It is the sum total of the masses of all the subatomic particles in that body.
– Matter occupies space and can be solid, liquid or gaseous.
– Unless matter is added to or removed from a body, the mass of that body never varies.
– It is constant under all conditions. There are as many atoms in a kilogram of, say, metal on the moon as there are in the same kilogram of metal on planet Earth. However, that kilogram of metal will weigh less on the moon than on planet Earth
– The basic unit of mass is the kilogram (kg). The most commonly used multiple of this basic unit is the tonne (1000 kg) and the most commonly used sub-multiple is the gram (0.001 kg).