What is the repeating unit of a polymer called?

The repeating unit of a polymer is called a monomer. A monomer is a small molecule that can join with other similar or identical molecules to form a larger structure known as a polymer. For example, in the case of polyethylene, the repeating unit (or monomer) is ethylene. When many ethylene units are chemically bonded together, they create the polymer polyethylene.

Understanding the role of the monomer is crucial in polymer chemistry, as it is the building block that defines the properties and characteristics of the resulting polymer. In contrast, a macromolecule refers to a very large molecule typically made up of thousands of atoms, which includes polymers but is a broader term. A polymerase is an enzyme that synthesizes polymers, particularly nucleic acids or proteins, and a composite refers to a material made from two or more constituent materials with significantly different physical or chemical properties.