What are bi-functional and tri-functional monomeric units????

Define with xamples....

Bi-functional and tri-functional monomeric units are the monomeric units which contain two and three functional groups respectively. These functional groups can be either same or different. For example Nylon 6, 6 − Formed by the condensation of hexamethylene diamine with adipic acid

the monomers, hexamethylene diamine and adipic acid, both contain two functional groups each. Hence they are bi-functional monomeric units.