The terms polymer and macromolecule do not mean the same thing. A polymer is a substance composed of macromolecules.
The latter usually have a range of molar masses (unit g mol-1), the distributions of which are indicated by dispersity (Đ). It is defined as the ratio of the mass-average molar mass (Mm) to the number-average molar mass (Mn) i.e. (Đ) = Mm/Mn.4 Symbols for physical quantities or variables are in italic font but those representing units or labels are in roman font.