The mass (in grams) per mole of its entities (atoms, molecules). It's numerically equal to atomic/molecular weight but expressed in g/mol instead than atomic mass units(u).
The unit used in chemistry to count entities at the atomic/molecular level.
The mass of an atom, usually expressed in atomic mass units.
The sum of the atomic weights of all atoms in a molecule; it's similar to molar mass but doesn't account for multiple molecules or compounds.