English makes use of passive and active to express how an action is viewed. Compare:

• Apple unveiled the iPhone 6 in September 2014.
• The iPhone 6 was unveiled in September 2014.

Notice in the second example how iPhone 6 becomes more important in the sentence and some information (the agent Apple) can be left out.

 Form

The passive comprises two parts: be + 3rd form (also known as the past participle or -ed participle). Examples:

• They are paid monthly. (present simple passive)
• They have not been paid yet this month. (present perfect simple passive)
• They were paid on time last month. (past simple passive)
• An additional 327 self-catered bed spaces are currently being constructed within the boundaries of Hiatt Baker. (present continuous passive)
• Key texts for taught courses can be borrowed during fixed loan periods and must be returned to the Issue Desk. (modal passive)
• 'At Bristol there's a great balance between studying what you find interesting in literature and being presented with brand new and exciting ideas in every lecture and seminar.' (-ing form passive)

In all of the above examples, the agent (the person or thing 'doing' the action), has been left out. Decide who or what the agent might be in each case, and why they were left out.

Passives are common in academic writing. While not all verbs can naturally be used in both the active or the passive, often a writer can make a choice as to which to use.

Impersonal Language

One reason is in order to sustain an impersonal or neutral tone which is a feature of academic style.

• In the past two decades, the risk of catastrophic fire has increased, which is widely believed to be a result of climate change. (many people think)
• The airline Fly-me was expected to announce ten new routes from Bristol Airport to new destinations. ... Fly-me was understood to be on the verge of announcing ten new routes from Bristol. (people expected, people thought)

Audience and Purpose

Study these headlines from three different national newspapers: 

1. EDF have dismissed 400 construction workers
2. 400 construction workers have been dismissed by EDF
3. 400 construction workers have been dismissed

In the examples above, the writers have made different choices as they are writing for different audiences (i.e. the type of people who buy their paper), even though each is reporting the same news story. Why might the writers have chosen to use the active or passive, or to include the agent?

In Headline A, the active may have been chosen to emphasise that EDF is responsible for the action.

Headline B employs the passive, and emphasises the workers who have lost their jobs; Headline C does not mention the company at all, and uses the agentless passive. This places no emphasis on the agent doing the action (that is, EDF). Although these sentences describe the same action, the change in emphasis is important.

Given ... New

The passive is also used to ensure that the main topic of the text (polio in the examples below) remains the subject of the sentences. This satisfies the expected order that information should come in a text. Compare:

• Polio used to cause severe illness in millions of people around the world. Today, it has been almost eradicated thanks to a vaccine.
• Polio used to cause severe illness in millions of people around the world. Today, a vaccine has almost eradicated it.

The flow of ideas across sentences is usually easier for the reader to process when the 'new' information (vaccine in the examples above) is presented at the end, after the 'given' information, polio.