Descriptive of a population of polymers in which all individual molecules have the same covalent structure and molecular size. It is contrasted with polydisperse, descriptive of a population of polymers that have the same repeating unit(s) and the same covalent structure, but vary in molecular size. Paucidisperse describes a population of related polymers that share the same basic covalent structure, and perhaps function, but show a low level of dispersity. Microheterogeneous describes a population of polymers with the same primary structure, and possibly the same molecular size, but with limited modifications of some monomeric units.