In many sentences you will find an agent (the person or thing who does something) and a recipient (the person or thing that something is done to). If we want to make the agent the subject, we use active verb forms.
- The storm damaged our roof.
- The children have stuck chewing gum all over the carpet.
- Somebody has picked my pocket.
- The dog bit the boy.
If we want to make the recipient the subject, we use passive verb forms.
- Our roof was damaged in the storm.
- Chewing gum has been stuck all over the carpet by the children.
- My pocket has been picked (by somebody).
- The boy was bitten by the dog.
If we want to make something else the subject, we usually use a structure with have + object + past participle.
- We had our roof damaged in the storm.
- The carpet has had chewing gum stuck all over it by the children.
We can usually decide what the subject should be by choosing the right verb.
Compare:
- The retail chain employs over a million people. (Subject – the retail chain; verb – employs)
- Over a million people work for the retail chain. (Subject – over a million people; verb – work)