monomer

n. simple chemical compound of low molecular weight that can be polymerized

A monomer (from Greek mono "one" and meros "part") is a small molecule that may become chemically bonded to other monomers to form a polymer. Examples of monomers are hydrocarbons such as the alkene and arene homologous series. Here hydrocarbon monomers such as phenylethene and ethene form polymers used as plastics like polyphenylethene (commonly known as polystyrene) and polyethene (commonly known as polyethylene or polythene). Other commercially important monomers include acrylic monomers such as acrylic acid, methyl methacrylate, and acrylamide.
See more at Wikipedia.org...

Noun
1. a simple compound whose molecules can join together to form polymers
(hypernym) compound, chemical compound

n. monomer, simple chemical compound of low molecular weight that can be polymerized

adj. (Chemistry) monomeric, of monomers, pertaining to molecules capable of combining with other molecules to produce polymers; (Biology) composed of one part or created from one piece

A small molecule that is linked with large numbers of other small molecules to form a chain or a network (polymer).