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!