Active Voice: When you use an active voice, the subject of the sentence is doing the verb.
For Example, “The girl shovels the snow.”
The action can take place in the present, past, future, present progressive (is taking), past progressive (was taking), future progressive (will be taking), present perfect (has taken), past perfect (had taken), future perfect (will have taken).
Passive Voice: When something is done to the subject of the sentence. You can recognize it because it includes the helping verb to be.
For Example, “The book is read by the student.”
Summary: Writers know it is almost always preferable to write in the active voice, but sometimes the passive voice sneaks in. That is what editing is for. The active voice is important because it focuses on the subject rather than the object of the verb.
For Example, “The woman gardened all day” vs. “The flower bed was tended to by the woman”
The woman (the subject) is the focus of the active voice sentence, whereas the flower bed is the focus of the passive sentence.
Passive voice sentences often sound clunky or awkward so they are not too difficult to spot in your work, but when doing a line edit you should pay special attention to the verbs.
If you have studied another language, you probably agree that the verbs are the most complicated thing that you must learn. Not at all surprisingly that is true of English, even if you grew up speaking it.
Just because you are using the verb to be does not mean you are using the active voice. It is only when it is the helping verb that it changes the voice from active to passive.
The present perfect and past perfect tenses are not the same as the passive voice. This is a surprisingly common misconception. Overusing these two tenses in your writing can make it weaker, but using them infrequently can strengthen your writing as long as you make sure you have used them correctly.
When to Use the Passive Voice:
The passive voice is helpful when you want to emphasize the object of your sentence rather than the subject. You can also use it to slow down the action in the novel in order to focus on the scene. Some writers even mix in the passive voice very occasionally to vary their sentence structure, but it takes practice in order to do this effectively.
An example of using the passive voice to emphasize the object of your sentence:
Abraham Lincoln was assassinated by John Wilkes Booth
The sentence makes the assassination about Lincoln (the object) as opposed to the person who committed the crime (the subject).