SUMMARY
Sentential complements occurring with prepositions in English are traditiona ly known as gerunds, verbal forms in -ing having the functions of both nouns and verbs.In transformational-generative grammar they are interpreted as ,embedded sentences in the underlying structure containing their own subject, which may be either deleted under coreference with the subject of the matrix sentence or overtly expressed, as in 1. (a)John is happy about leaving (b) John is happy about Mary leaving.