- The base form of the verb can be used with imperative ( ie "commanding" ) force. For example: Stop doing that! / Be quiet! / Please go away! / Look what you've done!
- Imperatives never have perfect aspect but may have progressive aspect – eg Be waiting there at 3pm.
- To form the negative, the "dummy operator" Do is used, followed by the negative particle not and infinitive: Do not disturb. / Don't be stupid. / Don't look at me like that!
- Do can also be used to add extra emphasis or force to an affirmative imperative, very often also preceded by Oh, in spoken English : Do stop doing that! / Oh, do be quiet!/ Oh, do go away!
- In all the examples above, the imperative force can be seen as expressing an order (eg Be quiet! / Do not disturb) or admonition (eg Look what you've done! Don't be stupid!). It expresses the wish or attitude of the person issuing the command.
- However, the imperative is also used to express "commands" which are for the benefit of the receiver : Come in and take a seat. / Do help yourself. / Lightly whip the cream... / Don't worry.
It therefore expresses functions such as:
- invitations : Come in and take a seat. / Do help yourself
- instructions : Lightly whip the cream...
- reassurance : Don't worry.
Parrott, M. Grammar for English Language Teachers, Cambridge
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