英语动词按其构成动词词组时所起的作用可分为主动词(main verb)和助动词(auxiliary)两大类。主动词,又叫实义动词(lexical verb),是动词词组的中心词(head),必不可少。而助动词则必须与主动词连用,才能构成动词词组。虽然助动词在表达语义方面所起的作用不如主动词,但是在语法方面它所起的作用是相当大的。上几讲我们谈及的不少语法形式都要借助于它。助动词的部分用法比较微妙,不太容易掌握,因而需要特别注意。助动词分为三类。第一类是基本助动词(primary auxiliary),包括 be,do, English verbs can be divided into two main categories: main verbs and auxiliary verbs. The active word, also called the lexical verb, is the head of the verb phrase and is indispensable. The auxiliary verb must be used in conjunction with the active word to form a verb phrase. Although auxiliary verbs play less of an active role in expressing semantics, their role in grammar is considerable. Many of the grammatical forms we talked about in the last few talks require it. Some use of auxiliary verbs is subtle and not easy to grasp, and requires special attention. Auxiliary verbs fall into three categories. The first category is primary auxiliary verbs, including be, do,