oligomer

Quaternary state of a protein ( usually, although it can apply to other larger molecules, biological or synthetic ) where more than one polypeptide chain assembles to create the final unit. The opposite of a monomer. Oligomer usually suggests some sort of order to the assembly process. A random assembly of proteins is instead called an aggregate. Some common types of oligomers include:

• polymer such as actin or tubulin
  
• dimer where two proteins get together. If the two proteins are the same, it is a homodimer, if different, a heterodimer
  
• homo/hetero - trimer, tetramer, pentamer, hexamer and so on.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.