In a passive sentence, the person or thing acted on comes first, and the actor is added at the end, introduced with the preposition "by." Sometimes, the actor is completely omitted.
When to use passive voice?
In some sentences, passive voice can be perfectly acceptable. You might use it in the following cases:
1. When the agent of the action is unknown:
“The bank was robbed yesterday.” (We don’t know who robbed the bank)
2. When the agent is unimportant:
“The sports hall was renovated two months ago.” (The people who renovated the hall are unnecessary information)
3. When the agent of the action is definitely clear:
“My uncle was born forty years ago.” (Everyone knows that it was her mother who bore him)
4. To emphasize the recipient of the action:
“Addie was appointed the captain of his class.” (The students who appointed Addie are not the ones to emphasize)
5. To connect ideas in different clauses more clearly:
“The cell phone was being used for playing games by the kid during the lesson, who was then asked to turn it off. “
6. To make generic statements, announcements, and explanations:
“The passengers are asked not to use the communication gadget during the flight. “
7. To be used in lab reports and scientific papers:
“A reference sample is then analyzed to create the individual's DNA profile.”
When to avoid passive voice?
In writing, passive sentences can be vague about who is responsible for the action:
“Paper has been submitted prior to the test.” (Who submitted the paper?)
“America was discovered in the fifteenth century.” (Who discovered America?)
“Since the motorcycle was ridden by Sam, the damages during the accident should be paid for by him.” (Wordy and indirect)