The hierarchical order can be best illustrated with a tree diagram of constituent structure.
In addition, the hierarchical structure of sentences can also be illustrated by using brackets and subscript labels.
8、Lexical categories 词类
Words are organized into groups of lexical categories, commonly known as parts of speech. A language has major and minor lexical categories. Major lexical categories are open categories that new words are constantly added. Minor lexical categories are closed categories because the number of the lexical items in these categories is fixed and no new members are allowed for. English has four major lexical categories and six minor lexical categories.
所有的词都有某种属性，即词性。词可以分为主要词类和次要词类。主要词类不断有新词加入，它是开放词类，而次要词类是封闭的，因为这类词的词项是固定的，不允许有新词加入。
英语有四个主要词类和六个次要词类。
主要词类：
Noun (N) 名词：student
Verb (V) 动词：like
Adjective (Adj) 形容词：tall
Adverb (Adv) 副词：loudly
次要词类：
Determiner (Det) 限定词：the, a, this, his
Auxiliary (Aux) 助动词：can, do, will
Preposition (Prep) 介词：in, at, over
Pronoun (Pron) 代词：he, she, us, mine
Conjunction (Conj) 连词：and, or, but, while
Interjection (Int) 感叹词：oh, ah, eh