Generally, try to use the active voice whenever possible. Passive voice sentences often use more words, can be vague, and can lead to a tangle of prepositional phrases.
In a sentence written in the active voice, the subject of sentence performs the action. In a sentence written in the passive voice the subject receives the action.
Active: The minister believes that Parliament must place a ceiling on the budget. Passive: It is believed by the minister that a ceiling must be placed on the budget by Parliament.
Active: Researchers earlier showed that high stress can cause heart attacks. Passive: It was earlier demonstrated that heart attacks can be caused by high stress.
Active: The bat hit the ball. Passive: The ball was hit by the bat.
Here are some tips and strategies for converting sentences from the passive to the active voice.
Look for a “by” phrase (e.g., “by the bat” in the last example above). If you find one, the sentence may be in the passive voice. Rewrite the sentence so that the subject buried in the “by” clause is closer to the beginning of the sentence.
If the subject of the sentence is somewhat anonymous, see if you can use a general term, such as “researchers,” or “the study,” or “experts in this field.”
There are sometimes good reasons to use the passive voice.
After long debate, the proposal was endorsed by the long-range planning committee.
The data processing department recently presented what proved to be a controversial proposal to expand its staff. After long debate, the proposal was endorsed by . . . .
The procedures were somehow misinterpreted.
Every year, thousands of people are diagnosed as having cancer.
Visitors are not allowed after 9:00 p.m.