The voice you write with influences the tone of your writing. Too much passive voice can make writing seem dull and flat, which is why active voice is generally encouraged in most writing. While many students use the grammar check features provided on computers to check their work, programs such as Microsoft Word do not recognize all instances of passive voice.

Effect on Subject

When a sentence is written in active voice, the subject performs the action. For instance, in the sentence, “Sarah sang the song,” Sarah performed the action. However, when a sentence is written in passive voice, the subject does not perform the action. Instead, the subject receives the action. For instance, in the sentence, “The song was sung by Sarah,” “song” is the subject, but it received the action from Sarah rather than performing it.

Recognizing Passive Voice

You can recognize passive voice in a sentence because it always includes a form of “be,” such as “am,” “is,” “been,” “was” and “were.” This does not necessarily mean that just because a sentence has a “be” form verb in it that it is in passive voice. Sentences that include passive voice often include a prepositional phrase, such as “by the…”, just after the verb. The doer of the action is the object of the prepositional phrase. For example, in the sentence, “Sue was bitten by the dog,” “Sue” is the subject, and the “dog” is performing the action.

When to Use Passive Voice

Active voice is generally considered better than passive voice, because it makes sentences shorter, more direct and more clear and concise. This doesn’t mean passive voice is always inappropriate. Use passive voice when it is rhetorically effective to provide an indirect expression, as when the doer of the action is unknown, the doer isn’t as important as the receiver and the doer is someone you don’t want to name. For instance, if you don’t know who left the lights on, you would write, “The lights were left on.” If you write about police being alerted to a prison break, you could use passive voice in the sentence “Police are being notified that prisoners escaped,” rather than the active voice in "The dispatcher is notifying police that prisoners escaped.” That's because the dispatcher’s action is not as important as the police receiving the information. When you don’t want to place any blame on one person, you could use passive voice, as in the sentence “I was provided the wrong directions.”

Changing Passive to Active

To change passive voice to active voice, determine who or what is performing the action, make it the subject of the sentence and change the verb accordingly. For example, to change “Sue was bitten by the dog” from passive voice to active voice, write the following: “The dog bit Sue.” You might have to infer who or what is performing the action if it isn’t stated. For instance, in the sentence “Test results will be given after the tests are graded,” it is not stated who will give the test results. Yet, you can infer that “Teachers will give test results after the tests are graded.”