The active voice has a strong, direct, clear tone, whereas the passive voice is weaker and subtler. Active language is often easier to understand, and also makes it clear who is doing what.

However, there is nothing wrong with the passive voice per se. Passive voice can be useful and appropriate in some cases. The problem is its overuse in some types of writing, such as in academia or government.

Good writing will have a balance of active and passive language.

The difference between active and passive voice

An active sentence is one in which an agent or actor (subject) does something (verb) to a person or thing (object):

The professor [subject] wrote [verb] a textbook [object].

For a passive sentence, the reverse is true – the subject has something done to it by an agent:

The textbook [subject] was written [verb] by the professor [agent].

Passive voice is often used because it takes the agent out of the process, making the text sound more ‘objective’. Often, the agent is not even specified:

The ball was kicked. [by whom?]

Experiments were conducted [by whom?] to test the humidity of the cabinet.

An increased level of salinity was observed. [by whom?]

In the past, in an effort to appear objective or to avoid saying who was doing things, researchers and government staff institutionalised this style as the ‘correct’ way to write:

The study was conducted over 3 months.

The funding to the program was cut.

Activate your language

There are many benefits to ‘activating’ your writing. Active language is easier to understand; it is usually shorter, livelier, clearer and more like normal speech. It also makes it clear who is doing what.

For example, a recommendation that specifies the proposed agent for the task is much more likely to get some action than one that is vague on who is going to do what:

A committee should be appointed to investigate the use of the passive voice in government publications.
becomes
The Editing Advisory Group should appoint a committee to investigate the use of the passive voice in government publications.

A passive sentence can be made active by adding an agent:

The humidity of the cabinet was tested.
becomes
We tested the humidity of the cabinet.

The textbook was written.
becomes
The professor wrote the textbook.

However, active sentences do not always need to start with a person or organisation:

Serotonin levels increased.

When changing passive to active constructions, take care not to change the meaning, particularly in sentences that use can, could, will, would or might:

The series of experiments could lead to the mechanism being identified. [passive; means that it might happen]
versus
The researchers will identify the mechanism through a series of experiments. [active; means that it will definitely happen, so the meaning has been changed]
or
If the experiment works, we will attempt to identify the mechanism [active; means that it might happen, so the meaning is not changed]

If you are struggling to make a passive sentence active (e.g. if the sentence becomes cumbersome), it is probably best left as passive:

About 200 people were hospitalised with healthcare-associated infections.
versus
The healthcare system was responsible for the hospitalisation of 200 people with infections. 
[Apart from being cumbersome, this sentence reconstruction also takes the emphasis away from the number of people who were infected, which you might not want to do.]

Other reasons to keep the sentence passive are when you want to emphasise a certain point (as in the example above), or when the actor is unknown, unimportant or generic:

Rules are made to be broken.

All people are created equal.

These things are sent to try us.

Here are some examples of the conversion of passive to active:

Original (passive)Rewrite (active)
The recommendations were considered by the department.The department considered the recommendations.
To compare treatments, patients were randomised into 2 groups, and were given either treatment A or treatment B.To compare treatments, we randomised the patients into 2 groups and gave them either treatment A or treatment B.
The report was finalised by the working group in 2014 and was submitted to the advisory board.In 2014, the working group finalised its report and submitted it to the advisory board.
The 5 Moments for Hand Hygiene should be followed if you are a healthcare worker.Healthcare workers should follow the 5 Moments for Hand Hygiene.
The national meeting was attended by representatives of the agriculture industry and all levels of government.Representatives of the agriculture industry and all levels of government attended the national meeting.
To determine whether biodiversity had decreased in the region during the past 10 years, the number of species was identified and counted.We counted and identified the species in the region to determine whether biodiversity had decreased during the past 10 years.
The decision was based on expert opinion.Expert opinion formed the basis of the decision.
[Note: This sentence is probably best left in the passive voice.]

Check for passive voice

Word-processing programs can be set to identify passive sentences (e.g. Microsoft Word can be set to underline passive sentences) so that you can see how often you are using the passive voice.