trimer

from WordNet (r) 3.0 (2006)
trimer
    n 1: a polymer (or a molecule of a polymer) consisting of three
         identical monomers
    
from The Collaborative International Dictionary of English v.0.48
oligomer \o*lig"o*mer\, n. (Chem.)
   A molecule composed of a small number of linked monomer
   units; a short polymer; -- compounds called oligomers have
   less than one hundred monomer units and usually less than
   thirty. Oligomers of increasing length are called {dimer},
   {trimer}, {tetramer}, {pentamer}, {hexamer}, {heptamer},
   {octamer}, {nonamer}, {decamer}, etc. In colloquial
   laboratory jargon, they may also be referred to as
   {nine-mer}, {ten-mer}, {eleven-mer}, {twelve-mer}, etc.,
   especially for oligomers of greater than eight units.
   [PJC]
    

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