Introduction Grammatical hierarchy(语法层次) Grammar is the structural system of a language. The grammar of the English language is organized into five ranks:the sentence,the clause,the phrase,the word,and the morpheme. Each rank is composed of one or more than one grammatical unit of the immediate lower rank. Thus the sentence is a grammatical unit that consists of one or more than one clause;the clause,one or more than one phrase;the1 Introduction Grammatical hierarchy(语法层次) Grammar is the structural system of a language. The grammar of the English language is organized into five ranks:the sentence, the clause, the phrase, the word, and the morpheme. Each rank is composed of one or more than one grammatical unit of the immediate lower rank. Thus the sentence is a grammatical unit that consists of one or more than one clause; the clause, one or more than one phrase; the