The Active

We say things in the active voice when we want to show who or what has done something. In the active voice the agent (the person or thing that does something) becomes the subject of the sentence.

For example:

"She cleaned the office." (Who cleaned the office? She did=the subject)

"He stole my car." (Who stole my car? He did=the subject)

The Passive

The passive voice is used when the subject of a sentence is the person or thing affected by the action of the sentence.

We particularly use the passive voice when we don't know or aren't bothered exactly who has done something. This is called passive without agent where the recipient of the action becomes the subject.

For example:

"The office was cleaned." (What was cleaned? - The office=the subject)

"My car was stolen." (What was stolen - The car=the subject)

We often use the passive to report what someone has said but avoid who said it.

For example:

"I was told he wasn't coming."

"You were asked to bring some wine to the party."

Sometimes you may want to use the passive voice but wish to mention who carried out the action. This is called passive with agent and the agent is usually introduced with the word by.

For example:

"The office was cleaned by Mrs Smith."

Or you may use a subject such as people, someone, they etc, when you don't know who the agent is.

For example:

"The car was stolen by joyriders."

When you can't use the passive

Intransitive verbs cannot be used in the passive. This is because they cannot have objects, and so there is nothing to become the subject of the passive sentence. For example with verbs like die or arrive.