When writing, active voice is when the subject of a sentence performs the action in the verb, while passive voice is when the subject has the action performed on it. An example of a sentence using the active voice is "She reads a book." This sentence written in the passive voice is "The book is read by her."
Most non-scientific writing uses the active voice rather than the passive voice, states Purdue University. This helps make the sentences less complicated and clearer for readers. Overuse of the passive voice could make the writing seem less interesting.
In scientific writing, the passive voice is used so researchers can avoid personal pronouns and specific names. This helps the writing remain fact-based and objective. However, too much use of the passive voice can make the meaning difficult to understand.
If there are too many sentences with passive voice, writers can change a few to the active voice. This is done by determining who or what is performing the action. Typically, writers can identify this by the phrase "by the" that comes after the verb; the object of the phrase is performing the action. For example, in the sentence "The ball was caught by the dog," the dog is performing the action of catching. This sentence rewritten in the active voice is "The dog caught the ball."