Step-growth polymerization includes polycondensation and polyaddition. Polycondensation is a kind of polymerization whose chain growth is based on condensation reaction between two molecules with various degree of polymerization. The typical example are polyesters, polyamides and polyethers. It is sometimes confused by condensation previous definition of condensation polymerization. Polyaddition is a type of step-growth polymerization of which chain growth is based on addition reaction between two molecules of various degree of polymerization. The typical example for polyaddition is the synthesis of polyurethane.