When to Use Active Voice vs. Passive Voice

A sentence is in active voice when the subject is the one performing the verb’s action.

The girl has written a letter.

Most English sentences with an action verb are written in the active voice. However, it is possible to change the word order of some active sentences to render them passive sentences. A sentence is in passive voice when the subject is being acted on by the verb.

The letter has been written by the girl.

What is Voice?

English verbs have five properties: voice, mood, tense, person, and number. There are two grammatical voices: active and passive. Active voice means that the subject performs the verb’s action, while passive voice means that the verb is acting upon the subject. The same content can often be written in both active voice and passive voice.

We fabricated the composites in a clean room. (active)
The composites were fabricated in a clean room. (passive)

The active voice emphasizes the subject, or the thing performing the action. The passive voice, on the other hand, emphasizes the action or the recipient of the action. Schools typically teach students to avoid the passive voice whenever possible. This is because sentences in active voice tend to be stronger and more concise. However, the passive voice can be more appropriate depending on the context. The passive voice is also useful when you want to avoid using the first-person pronoun in academic writing.

Active vs. Passive Voice in Research Writing

Differences Between Active and Passive Voice

What is the active voice?

As mentioned above, a sentence is in active voice when the subject is performing the verb’s action.

We collected the samples.

Here, the subject is “we,” the verb is “collected,” and the object is “the samples,” so the sentence structure is subject-verb-object or performer-of-action + action + recipient of action.
This is the active voice structure. Sentences in active voice are often more direct and concise than the same sentences in passive voice. As such, the active voice is preferable to passive in most situations.

What is the passive voice?

A sentence is in the passive voice when the verb is acting on the subject. The passive voice emphasizes the action or the recipient of the action rather than the agent of the action. Certain passive sentences can omit the agent altogether.

The samples were collected by us.
The samples were collected.

The sentence structure here is recipient-of-action + action + performer-of-action. However, it is also possible to remove the “performer-of-action” to further emphasize the action and recipient of action. This recipient-of-action + action structure is often used in academic manuscripts.

When to Use the Active Voice

Sentences in active voice are generally stronger and more concise than their passive counterparts. As such, it is typically better to write sentences in the active voice. It is also best to use active voice when the emphasis of the sentence should be on the performer of the action.

She studied physics. (active)
Physics was studied by her. (passive)

Here, the second sentence is weaker and somewhat unnatural compared to the first. It can also be observed that the second sentence is wordier than the first.

We developed a novel method of fabricating gold composites. (active)
A novel method of fabricating gold composites was developed. (passive)

The first sentence here stresses that “we” developed a novel method; the second sentence, on the other hand, emphasizes the developed method itself.

It is important to note that only sentences containing direct objects can be changed to passive voice.

Active (Correct)
The cat sat on the table.
Passive (Incorrect)
The cat is sat on the table.

This sentence does not have a passive alternative because it does not have a direct object--”on the table” is a prepositional phrase and not a recipient of the action.

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When to Use the Passive Voice

Sentences in passive voice are often wordy and unnatural compared to their active counterparts. They can also lead to a mess of prepositional phrases. However, because the passive voice emphasizes the recipient of an action or the action itself (rather than the agent of the action), it can be preferable in certain contexts.

(1)When placing emphasis on the action or the recipient rather than on the agent

Ten samples were collected.

The emphasis here is on the samples and the fact that they were collected, not on who collected them.

(2)To avoid naming the agent

Several errors were overlooked.

Using the passive voice here allows the person who overlooked the errors to remain unidentified. As such, passive voice sentences are often used to avoid an accusatory tone and maintain tactfulness when pointing out mistakes.

(3)When the agent is unknown (or unimportant)

Cynthia’s home was robbed last month. The police have not yet narrowed down the suspects.

Here, the person who robbed Cynthia’s home has not yet been identified, so using the passive voice is sensible. The active alternative would be “Someone robbed Cynthia’s home last month.” This places a greater emphasis on the unknown person who robbed Cynthia rather than the fact that Cynthia was robbed.

(4)When adopting an authoritative tone

Boarding the train without a face covering is not permitted.

(5)To keep the focus consistent throughout multiple sentences

Group 2 collected the samples. The samples were then analyzed by Group 1 using HPLC.

Using the passive voice for the second sentence of the above example allows the two sentences to maintain the same focus; the two sentences together focus on the samples rather than on the individual groups that collected and analyzed them.

How to Change Passive Voice to Active Voice in Sentences

As mentioned above, active voice sentences that have direct objects can be changed into passive voice sentences. An active voice sentence has the structure performer-of-action + action + recipient-of-action; a passive voice sentence has the structure recipient-of-action + action + performer-of-action. Therefore, a sentence can be changed from active voice to passive voice simply by reordering its elements.

We administered increasingly potent concentrations. (active)
Increasingly potent concentrations were administered (by us). (passive)

To change a sentence from active voice to passive: (1) The direct object switches location with the subject. (2) The subject “we” changes in form and is placed into a prepositional phrase beginning with “by.” (3) The main verb “administered” changes in form, and the auxiliary verb “be” is added.

A passive voice sentence can be changed into an active voice sentence by reversing these steps: (1) The subject is now the direct object. (2) The preposition “by” is removed, and its object is now the subject. (3) The main verb form is changed, and the auxiliary verb “be” is removed.