oligomer

An oligomer is a molecule that consists of a few monomer units, in contrast to a polymer that, at least in principle, consists of an unlimited number of monomers. Dimers, trimers, and tetramers are oligomers.

Many oils are oligomeric, such as liquid paraffin. Plasticizers are oligomeric esters widely used to soften thermoplastics such as PVC. They may be made from monomers by linking them together, or by separation from the higher fractions of crude oil. Polybutene is an oligomeric oil used to make putty.