In chemistry, bifunctionality or difunctionality is the presence of two functional groups in a molecule.
A bifunctional species has the properties of each of the two types of functional groups, such as an alcohol (−OH), amide (−CONH2), aldehyde (−CHO), nitrile (−CN) or carboxylic acid (−COOH).
Many bifunctional species are used to produce complex materials.
They participate in condensation polymerization like polyester and polyamide.
Polyfunctional species have more than two functional groups.