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Language Focus: Active and Passive Voice

The active and passive voice are important in English. In this article, learn how to use them correctly.


We use the passive voice when we want to describe an action, but it doesn’t matter – or we don’t know – who or what does/did it (called the agent).

If you really want to add the agent, you can put it after by at the end of the clause:

The item is then placed in the correct bin by the robot.
However, most of the time, it’s better not to include by + agent because if it’s really that important, you should probably just use the active voice:
The robot then places the item in the correct bin.

How do we form the passive voice?

We make the passive voice using the chosen tense of the auxiliary verb be followed by the past participle (e.g. used, taught). The verb be changes depending on the tense being used, but the past participle doesn’t.
The passive voice can be used in the same tenses the active voice, including the present simple, past simple and present perfect. However, in this step, we’re going to focus on using the passive voice in the present simple and with modal verbs.
Let’s look at how the present simple passive is formed:
Subject Correct form of be Past participle
Machine learning is used
The item is placed
Recycling centres are required
In the reading passage, there are also some examples of modal verbs used as part of a passive structure. Modal verbs, which include can, could, may, might, must, should and would, can be used in this way, but the form is a little different:
Subject Modal verb + be Past participle
The robot can be taught
A robot can be rented
To change the active voice to the passive voice, the object of the active verb becomes the subject of the passive verb. As we said above, the subject of the active verb isn’t usually needed in the passive structure.
Here’s an overview:
Subject Verb Object
The robot uses machine learning
Machine learning is used.  

How do we form the past participle?

To form the past participle, we usually just have to add ed or d to the end of the infinitive form of the verb. We only have to add d when the infinitive already ends with the letter e. If the infinitive end with the letter y, we first need to change it to i.
Here are some examples:
use > used
place > placed
require > required
rent > rented
rely > relied
However, for some verbs – irregular ones – the past participle doesn’t follow this pattern. For these verbs, you have to learn the past participle.
Here’s an example from paragraph 4 of the reading passage:
teach > taught
…the robot can be taught to identify pretty much anything that a human can.
You should make sure you learn the past participle form for the most common irregular verbs.

Verbs that can’t be used in the passive voice

You may have noticed that some very common irregular verbs aren’t included in the list above. That’s because they’re intransitive, which means they can’t have objects. If there’s no object, it can’t become the subject, so it’s impossible to make it passive.
Common verbs that can’t be used in the passive voice include be, said, go and become.
For example, in the reading passage, there’s an active sentence in paragraph 2 that uses the verb become:
Over time, it becomes smarter and more accurate.

There’s no object, so it can’t be made passive.


What do you find difficult about using the passive voice in English?

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English for STEM: Understanding Engineering Vocabulary

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