The term oligomer is derived from the Greek “oligos,” meaning “a few.” In chemistry, an oligomer is a short polymer consisting of approximately five monomer units, although agreement as to the strict length cutoff is debated and varies between four and one hundred. Oligomers are formed by oligomerization, which involves linking the monomer units together in a chemical reaction. Unlike a polymer, if one of the repeating units of oligomer is removed, its chemical properties may be significantly altered.
In biochemistry, the term oligomer is commonly used for short, single-stranded DNA fragments, used in hybridization experiments as primers. It can also indicate a short protein made of two or more subunits.