Roger Woodham replies:助动词do和have的用法

do, does, don't, doesn't

Present simple auxiliary verbs

The auxiliary do is used mainly to form questions and negative sentences with the present simple tense. It is not normally used in affirmative sentences.

It is also used in forming tag questions and shortened answers. Study the following examples:

• 'I enjoy cycling in the countryside, but I don't enjoy cycling in towns.'

• 'She doesn't play the ballgames that girls usually play, but she plays football.'

• 'You don't really like Helen, do you?' 'Of course I do! / No, it's true. I don't.'

• 'Do all cats drink milk?' 'Most do, some don't.'

• 'Doesn't he ever take a day off work?' 'He did once in 1999, but he hasn't so far this year!'

Do may be used in affirmative sentences, but when it is used in this way, it denotes strong contrastive emphasis with heavy word stress on the auxiliary itself.

Quite a lot of emotion is usually involved. Study the following examples:

• 'Do come in! Please don't stand there on the doorstep.'

• 'He thinks I don't love him, but I do love him with all my heart!'

• 'He's not a vegetarian! He does eat meat! I have seen him eat meat!

did, didn't

Past simple auxiliary verbs

Did and didn't are used as past simple 'helping' verbs in exactly the same way as do/don't and does/doesn't are used in the present simple.

Study the following examples:

• 'I played a lot of rugby as a young man, but I didn't ever play football.'

• 'You didn't forget to post my letter, did you?' 'Of course I didn't.

• 'Did he pass his exam?' 'He did, yeah!'

• 'I did remember to put salt into the dishwasher. It's not my fault that it's not working.'

have/haven't, has/hasn't, had/hadn't

Present perfect and past perfect auxiliary verbs

The auxiliaries have and had are used as 'helping' verbs in the construction of the perfect and past perfect forms of all main verbs. They are often pronounced as contracted weak forms in affirmative sentences and contracted weak forms are also used in the negative. Study the following examples and say them to yourself as you read them:

• 'They've been living in Calcutta for three years now, but they still haven't got used to the heat.'

• 'He's collected his medication from the chemist, but he hasn't actually taken any of the pills yet.'

• 'Have you seen my green pullover anywhere, Sandra?' 'No, sorry, I haven't.'

• 'This was a lie, for she'd borrowed his green pullover and had forgotten to return it.'

• 'They told me that they'd lived in Wiltshire all their lives, but had never visited Stonehenge.'

• 'We have paid for the flights, but we haven't paid the travel insurance yet.

Notice that in this last example there is strong contrastive emphasis, so the weak contracted form of have is not used in the affirmative part of the utterance. This equates to the emphatic use of do in the earlier examples.