Some teachers mark student's work as wrong if they use the passive voice. This structure is not a grammar error. It may not always be the best choice of style, but it is not an error.
What is the passive voice? Passive sentences are when the thing doing the action is not the subject of the sentence. Most English sentences are in the active voice and have the structure:
Subject -> Verb -> Object
Tom -- kicked -- the ball.
That is the thing doing the action -> The action -> The thing that receives the action
The passive voice reverses the usual structure.
The ball -- was kicked -- by Tom.
Why was the harbour crossed by the ferry?
The rice was eaten by Jane.
Why did the ferry cross the harbour?
Jane ate the rice.
The passive voice can be unclear. The main reason why some teachers dislike the passive voice is that they claim some such sentences leave out information. This is not a problem with the passive voice, but with the sentence writers leaving out information.
Her house was flooded.
This sentence does not tell us how the house was flooded. The argument is that since the sentence is in passive voice it is unclear. Did a water pipe break or was it a typhoon?
The broken water pipe flooded her house.
In this active voice sentence the problem is corrected and the sentence is much clearer. The problem with this argument is that the passive voice can still be used to provide all the information needed.
Her house was flooded by the broken water pipe.
The problem with the first sentence is not stylistic or grammatical; the problem is that information was left out. The passive voice sentence with all the information is slightly longer and that often is a sign of a poor choice of style. Style choice in this sentence is not an error.
Sometimes the passive voice is used for big generalizations and lazy thinking. The problem here is not the passive voice sentence structure. Instead the problem is weak thinking.
Immigrants are discriminated against.
This sentence is the kind of thing teachers disagree with. There is no discussion of which immigrants, where and why. The problem again is the lack of information, not the grammar or style of the sentence. The reader, or teacher marking the paper, will think that the writer does not understand the details of the topic. An active voice sentence can have as little information.
There was discrimination against immigrants.
It is important to be sure that your writing is informative and specific. So avoid large generalisations. It is argued that in homework assignments where you mention the work of an author you can improve your writing by not using the passive voice. Again the problem is using the passive voice to provide less information, not a problem with the passive voice as a style.
1997 is agreed to have been an important year.
Mary agreed that 1997 was an important year.
1997 is agreed by Mary to have been an important year.
The first sentence leaves out information. It is true that the example of an active voice provides more information and that the second passive voice sentence is a little longer. However if the active voice sentence only said "She agreed." then it would not be very informative.
In scientific writing the passive voice is often the required style. Lab reports should be written in an objective way that avoids using (the first person) "I".
Passive voice and the preferred objective style:
Sample A was added to the test tube.
Active voice and using "I" (less acceptable in a scientific paper):
I added sample A to the test tube.
When discussing the results either the active or passive voice can be used.
The safety of this chemical is shown by these results.
These results show the safety of this chemical.
Neither of these choices are wrong.
Sometimes the passive voice is the best choice. The passive voice is often used by people who are trying to avoid naming names, because it may be seen as admitting guilt, as making an accusation, as violating privacy or even endangering an undercover agent. It is easier in a passive sentence to leave out the person who did the action.
Oil was spilled.
The plans were recovered.
Company X spilled the oil.
The first sentence can be amended to include the company's name, ".., by Company X", but it is easier to leave the name out.
Agent ABC recovered the plans.
The passive voice tends to emphasise the object being acted on, not the person doing the action. In this sentence the "300 days" is emphasised, not the school.
Only 300 days were needed to build the school.
When the person doing the action is unknown a sentence in the passive voice is clearer.
26 homes were robbed in the housing estate.
A person or persons unknown have robbed 26 homes in the housing estate.
Does it really matter who is responsible for the action? Do you want to emphasize the receiver of the action instead of the one doing the action? If not put the one doing the action of the sentence in front of the verb.
Keep these tips in mind when you double check your work. If either the active or passive voice is better for your sentence rewrite it. Actively make choices about your writing. There is nothing grammatically wrong about using the passive voice. It is important to recognize when it would be better to, or better not to use the passive voice. Other than those occasions when your teacher just doesn't want you to, these choices are yours.
by John Larrysson
A native English speaker who has been teaching practical English in Hong Kong for more than a decade.