monomer

n.

1.

(Chem.) The basic conceptual building unit of a polymer; a molecule of low molecular weight which may combine with other molecules to form a molecule in a chain or branched form having high molecular weight; as, amino acids are the monomer units which are combined to form proteins; vinylic plastics are formed from monomers having a vinyl group.

Noun

1.

monomer - a simple compound whose molecules can join together to form polymers

chemical compound, compound