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  Passive - form (1)

We've just seen that we can express sentences in what we call active voice and passive voice. In active voice, subjects do what we have seen them do throughout this course - they are the person or thing doing the action. In passive voice though the subject is no longer the person or thing doing the action - it becomes the person or thing being acted upon. Let's look more closely now at how we form a passive clause or sentence.
Here's our original example again with the dog and the cat, first in active voice:
The dog chased the cat.
In this active sentence we have a subject (the dog) a past simple verb (chased) and a direct object (the cat). If we change this into a passive sentence we get this:
The cat was chased by the dog.
Let's break this sentence down and see what it gives us:
The cat was chased by the dog.
subject "be" past participle
Here's what we've done:
  1. Firstly, we've moved "the cat" to the subject position.
  2. Secondly, we've added the verb "be". We add the verb "be" in a passive sentence in the same form as the main verb in the active sentence. In our active sentence the verb was in the past simple (chased). So, in our passive sentence we need to add "be" in the past simple as well (was).
  3. Next, we add the past participle form of the main verb. (As "chase" is a regular verb, the past tense form that we saw in the active sentence and the past participle form are the same - "chased").
  4. Finally, we can show who did the action (the original subject) at the end, using "by". We can leave this part out though, and we'll have a look at why we might want to do that later in this unit.
Here's one way we can show clearly that "the cat" really is the new subject in the passive sentence. Let's replace "the cat" with "him" in our original sentence and see what happens when we make it passive again:
The dog chased him.
He was chased by the dog.
We've followed the same steps again and moved "him" to the subject position. But did you notice what happens when we move "him"? We've had to change it to the subject pronoun "he". So this confirms for us that the originalobject in the active sentence becomes the subject in the passive sentence.
Let's see how all this works with another example:
The mayor will open the new community centre. (active)
The new community centre will be opened by the mayor. (passive)
Breaking this down like we did before, here's what we get:
The new community centre will be opened by the mayor.
Subject "be" past participle
Once again the direct object (the new community centre) has become the subject. Next we have the verb "be" in the same form as the main verb in the active sentence. This time it's a future form with "will". After that we have the past participle of the main verb and finally we can show the original subject with "by" at the end.

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