Polyaddition is a step-growth polymerization process in which monomers react to form polymers without the loss of any small molecules. The monomers add to each other in a stepwise fashion, forming dimers, trimers, and eventually long chains. Polyaddition is often used to synthesize polymers with heteroatom linkages in the backbone, such as polyurethanes, polyethers, and polyamides.

聚加成是一种逐步增长聚合过程，其中单体反应形成聚合物而不损失任何小分子。单体以逐步的方式相互添加，形成二聚体、三聚体，最终形成长链。聚加成通常用于合成主链中具有杂原子键的聚合物，例如聚氨酯、聚醚和聚酰胺。