The research of Chinese complementizers like shuo and dao has important implications for both Chinese language studies and linguistic typology studies as well.

‘Whether’ is an interrogative adverb, serving as an interrogative specifier in an embedded clause while ‘if’ is an overt interrogative complementizer, introducing an embedded interrogative clause.

This article argues that "De"(的) in subject and object position in Mandarin Chinese can be a complementizer which has the feature .

Under the framework of Generative Grammar, the theory of complementizers can explain the features and usage of that , the theory about the licensing condition of the null complementizers can effectively explain the grammaticality of the that-less clauses.