Repeat unit

A repeat unit or repeating unit is a part of a polymer whose repetition would produce the complete polymer chain (except for the end-groups) by linking the repeat units together successively along the chain, like the beads of a necklace.

A repeat unit is sometimes called a mer or mer unit. "Mer" originates from the Greek word "meros," which means part. The word polymer derives its meaning from this, which means "many mers." A repeat unit (or mer), is not to be confused with the term monomer, which refers to the small molecule from which a polymer is synthesized.