Stylistic considerations for engineers

Passive and active voice

Passive and active voice simply refer to the relationship of the subject to the verb.

In a sentence using the active voice, the subject of the sentence (doer) performs the action described by the verb. Think of the subject as the “doer” of action.

Example:

• The student wrote the essay.

In the example above, the student is the subject (doer) of the sentence. The student directly performs the action of writing; therefore, the sentence utilizes an active construction. 

In a sentence using the passive voice, the subject of the sentence (doer) is acted upon by the verb. However, just because a sentence contains a past tense verb or a derivation of “to be” does not guarantee it is a passive sentence.

Example:

• The essay was written by the student.

In the example above, the subject (the student) receives the action of writing.

The subject (agent) is often dropped in passive sentences. The subject has become the object of the prepositional phrase, “by the student.” Accordingly, the subject can often be cut from passive sentences.

Example:

• The essay was written.

The sentence above is still passive, but the subject (student) has been removed.

We transformed an active sentence (The student wrote the essay) to a passive sentence (The essay was written by the student). Notice that although the student is no longer the subject in the passive sentence, it is still the main agent or “doer” of the sentence. Additionally, while “the essay” is no longer the direct object in the passive sentence, it is still the receiver of action. In other words, the functions of the subject and verb change, while their relationship to one another remain the same.

Transformations

Active to passive

• An object (typically the direct object) becomes the subject.
  1. The dog jumped over the log (direct object). (active)
  2. The log (direct object) was jumped over by the dog. (passive)
• A form of the “to be” verb is added to the main verb.
  1. The dog jumped (main verb) over the log. (active)
  2. The log was (“to be” verb) jumped over by the dog. (passive)
     1. “To be” verbs=am, is, are, was, were, will be, are being, were being, being, has, have been, had been, will have been
• If the original subject is mentioned, it becomes the object of the preposition “by.”
  1. The dog jumped over the log. (active)
  2. The log was jumped over by the dog (prepositional phrase beginning with “by” containing the object “the dog”).
     1. The majority of passive sentences drop this prepositional phrase, e.g. “The log was jumped over.”

Passive to active

• Determine the subject of the sentence.
  1. The flower was smelled by the girl (subject/agent/doer). (passive)
• Revise the sentence so the subject is performing the action, rather than just receiving the action.
  1. The girl smelled (subject “girl” is directly performing the action of “smelling”) the flowers.

When to use active voice vs. when to use passive voice

Using the passive voice can shift the focus of the sentence from the subject to the action. You should use the passive voice when it is more important to draw attention to the thing being acted upon. This is common in lab reports where you want to avoid the use of personal pronouns such as “I.”

Example:

• I poured twenty ccs of the solution into the beaker. (active)
• Twenty ccs of the solution was poured into the beaker. (passive)