Based on the above definitions of four-character structures, and considering the form of four-character structures in TCM, Ma guofan defines the four-character structures in a broad sense:“ the four-character structures, a unique language structure in Chinese, is a group of four characters in external form, and is relatively fixed in internal collocation, and is closely related in semantics which takes on a certain integrity and independence; it generally includes such forms as fixed idioms, conventionalized semi-fixed phrases, word groups, even one word and so on。”(Ma 189)

2。2。2 Characteristics of four-character structure

According to a number of scholars’ study, the characteristics of four-character structures can be summarized as follows:

1) From the point of linguistic form, four-character structures have neat and orderly antithesis as well as beautiful structure。 

2) From the point of contents, four-character structures only have a few words but have abundant connotation。 In the aspect of semantics, they have the advantages of unity and wholeness。