Le Système International d'Unités, or the International System of Units, which is the measurement system that is accepted worldwide, utilizing units measured in increments of 10.
The amount of a substance that contains as many particles as there are atoms in exactly 12 grams of Carbon-12.
6.022 x 10^23: The number of particles in exactly one mole of a pure substance.
gram molecular/formula mass
The mass in grams of one mole of a molecular substance.