本篇論文旨在研究中文"容易"，"好"，與"難"所屬的句式，內部結構，及此三者混淆難辨的原因。 　　我們認為"容易"屬Tough-結構，乃由Raising- 句主題化而來。"好"則屬Middle- 結構，是經詞彙律衍生而成。此分析正確的解釋二者表現之異同。 　由歷史演變觀之，"難"應屬Tough- 結構，為"容易"之反義詞。但因近代Middle- 結構興起，表面結構與Tough同，類化作用於焉產生，"難看"為一例。 / This study aims to identify the constructions of rongyi, hao, and nan sentencesin Mandarin, analyze their internal structure, and provide appropriate accountstoward the long-term confusion among these three. 　　Rongyi, in our analysis, is a gradable stative verb leading a tough construction.The so-called Tough Construction in Mandarin is a topicalized raising construc-tion with a generic subject. This analysis not only captures the generalization among similalr constructions (Raising Construction, Tough Construction, and topicalized sentences) but also accounts for its characteristics such as overtagent, long-distance binding, and so on. 　　Hao is a prefix triggering Middle Rule which surpresses all the theta-roles of atransitive active verb but the patient-like one (with the feature [-r]), yieldinga statve verb haoV as a middle predicate. The appropriateness of middles is subject to two pragmatic constraints, which further support our treatment of middle as a lexical process. The lexical approach successfully explains the surpressed agent, the inseparability between hao and V, and some other characte-ristics of middles. 　　Judging from diachronic evidence, nan is basically the antonym of rongyi and ap-pears in a raising construction, tough construction, and topicalized sentences as rongyi does. Analogy takes place, however, that in some cases, nan and its following verb are reanalyzed and undergo semantic shift due to its identical linear order with middleconstruction. That reflects the characteristics of languagechange.