段玉裁注《說文》，除詳明各字之形、音、義，間或論其對應之俗字，為數不尟，而經排比歸納，精研剺析，知其成因有六：一由隷變而成俗字，二由引伸義而別製俗字，三由用字叚借而成俗字，四由叚借義而別製俗字，五由俗寫殽譌而成俗字，六由以音之為用而滋生俗字。筆者列舉其例而剺析，知其本末兼具，體用並備。

Duan Yu-Cai annotated Shuo-Wen, not only with explaining the shape, syllable, and meaning of every word, but also with the popular character of them. The amount of popular character is huge. Through arrangement and generalization, popular character could be resulted from six ways. In this research, the author explains every method with many examples, and draws a conclusion that those methods gave enough consideration to basic and variation, structure and function in popular character.