In chemistry, an oligomer consists of a finite number of monomer units ("oligo" is Greek for "a few"), in contrast to a polymer which, at least in principle, consists of an infinite number of monomers.
In biochemistry, the term oligomer is used for short, single stranded DNA fragments, generally used in hybridization experiments (bound to glass slides or nylon membranes). It can also refer to a protein complex made of two or more subunits. In this case, a complex made of several different proteins is called hetero-oligomer . When only one type of protein is used in the complex, it is called homo-oligomer .