learn it! title
 Lots to do with 'do'
M Pedroso from Brazil asks:

M. Pedroso from Brazil asks: Why is the auxiliary verb do used in affirmative sentences like this: ‘I do believe in some things?
Roger replies:
You are quite right in suggesting that do is used as an auxiliary verb in questions and negative sentences, like these:
  • 'Do you like sugar in tea and coffee?'

  • 'Did you see Mary last night?'

  • 'What did she tell you?'

  • 'Did you do your homework?'

  • 'I like sugar in coffee but I don't like sugar in tea.'

  • 'I didn't do all my homework.'

  • 'I didn't see Mary.'

  • ' I didn't even phone her so she didn't tell me anything.'

Strong emphasis

You are also quite right in suggesting that do is not normally used in affirmative sentences. However, it is used when we want to place strong emphasis on what we are saying to show that we feel strongly about it in a positive way. In all these cases, do is pronounced with strong stress. Consider the following:

  • 'I do like sugar in my coffee! Loads of it!'

  • 'He does look smart in his new suit.'

  • 'You may not realise it, but I do love you.'

  • 'I did enjoy Sue's cooking last night. What a delicious meal she served us!

Contrastive emphasis

There are three other circumstances when do is used in affirmative sentences or clauses.

It is used for contrastive emphasis when we want to contrast one set of circumstances or point in time with another. Study the following:

  • 'I wish I could lose some weight.' 'Yes, well you do eat rather a lot of sweet things.'

  • 'Why didn't you ask him for a loan?' 'I did ask him, but he said he had no money.'

  • 'I hardly ever see my ex-wife, but I do see my children every week.

Polite Imperatives

It is sometimes used with imperatives when we want to make a suggestion or invitation more polite or welcoming. Study the following:

  • 'Do have some more strawberries! Help yourself!'

  • 'Do come in! Do sit down!'

  • 'Do be careful on holiday! Don't take any risks!'

  • 'Do write and tell us how you’re getting on!

Avoiding repetition

It is often used when we want to avoid repeating a verb which we have already used in the first part of the sentence. Consider the following:

  • 'Can I have another go with your game boy?' 'Yes, do!'

  • 'She said she’d help me with the ironing and she did!'

  • 'Did you see Maria when she was over in London?' 'Yes, I did!'