Auxiliary (verb): a verb that is used with another verb to show its tense, person, mood, etc.
? I. A classification of auxiliaries ? II. Similarities between primary auxiliary and modal auxiliary ? III. Use of primary auxiliaries ? IV. Use of modal auxiliaries ? V. Use of semi-auxiliaries
I. A classification of auxiliaries
? Primary auxiliary ? Modal auxiliary ? Semi-auxiliary
⊙Primary auxiliary(基本助动词): a verb that modifies the tense, voice or mood of another verb, or to express negative meaning, to form questions, or to express emphatic affirmative 表达主要动词的时态、语态、语气的词。
⊙ Modal auxiliary (情态助动词): an auxiliary verb that expresses modal meanings such as possibility, probability, desire, and constraint. 给谓语动词增添情态色彩，表示说话人对有关行为或事 物的态度和看法，认为其可能、应该或必要等的词。
⊙ Semi-auxiliary (半助动词): verbs between auxiliaries proper and main verbs. 介于助动词和主要动词之间的动词。
II. Similarities between primary auxiliary and modal auxiliary
1. 构成疑问句（一般general、特殊special、选择 alternative、附加tag），并对一般疑问句进行简 略回答。 (1) Do you often read English magazines? Yes, I do. No, I don’t. (2) Can you read English magazines? (3) We have tries our best, haven't we? (4) He needn’t come, need he?
1) 构成附加疑问的部分，须对陈述部分谓语的意义提出反 问，主语用相应的代词。 does he Your brother hardly watches TV, _________?
若句中有关部分为带否定前缀的词，该句仍视为肯定句。 wasn’t he He was unpleasant, _____________? 2) 陈述部分带有that引导的从句时，附加疑问句一般情况 下应该与主句谓语保持一致。但主句陈述部分是I think (I suppose, I believe …) + that时，附加疑问句部分则要和 that从句的主谓保持对应关系。 she She thinks that we will lose the game, doesn’t ___________? don’t you I think that you like it, ____________?
3) 附加疑问句有时用于祈使句，以缓和语气。 这时，附加疑问句通常用：will you, won’t you, would you。 will you (won’t you, would you) ? Shut the door, ________________________ 但否定的祈使句通常用will you。 will you ? Don’t forget it, _________
4) 附加疑问句有时也可用于向对方提出建议，或 征求对方的允诺。 这时附加疑问形式为shall we 。 shall we ? Let’s go for a walk, _________ shall we ? Let’s not talk about such matters, _________ will you Cf. Let us go for a walk, _________ ?
2. 构成否定句。 I don’t like classical music. 3. 代替前述动词。 does You speak English better than he ______. 4. 用于so，nor (neither) + 助动词或情态动词结构中， 代替前述句子的意义，表示“也”，或“也不”。 Mr. Huang speaks English well. So does Mr. Li. I