Grammar: Groups & phrases: Verb group: Structure of the verb group

Voice: active and passive

Difference between active and passive voice clauses

Most clauses in English are in the 'active voice'. In an active voice clause, the 'Subject' is also the 'Doer' of the main action, ie both Participants are expressed by the same noun group. In this example, the Subject and Doer are expressed by the noun group, the children:

The children chased the ghost around the flat.    Subject/Doer

Subject and Doer answer the question 'who/what did the action?':

However, if we ask 'who/what was the action done to?', a likely answer will be an elliptical clause in the 'passive voice':

In the passive voice clause, Subject and Doer are expressed by different noun groups. The person, animal, thing etc to whom the action was done (the ghost) is Subject, while the person, animal, thing etc who did the action (the children) is the Doer.

Another way of showing how active and passive voice clauses differ is to focus on Doer and Done-To :

Notice how Doer and Done-To change position in the clause when we change it from active to passive voice. 

We could also answer the question Who/what did the children chase around the flat? with an active voice clause, but in this case the information we are asking after, ie the ghost, needs to be stressed:

The emphasis on the ghost implies that the children might have been chasing other things. This contrastive meaning is a result of using an active voice rather than a passive voice clause. We can avoid this contrastive meaning by using the passive. 

In the passive voice clause the Doer of the action is expressed in a prepositional phrase by + noun group (by the children), but it is often omitted, either because it is considered unimportant to state the Doer or because speakers or writers do not want to be explicit about the identity of the Doer: 

Some speakers of English prefer not to use a passive voice clause because it is said to be impersonal, an impression that is strongest when the Doer of the action is omitted. However, there are contexts where the passive voice is appropriate, and it is therefore important that we understand the difference in the meanings expressed by active and passive voice.

This difference concerns how we organise the information in the clause. What matters most in English is what we put at the beginning and the ending of a clause respectively: the beginning of a clause expresses the Theme , and the ending of a clause expresses New Information . Active and passive voice clauses result in different elements being Theme and New Information respectively:

This pattern of information distribution in the clause means that a text is likely to have mainly active voice clauses if we want to make the Doer of the action our Theme, and the Done-To the New Information. This pattern is typically found in various types of stories because the Doer is usually the most important character or protagonist. 

On the other hand, a text is likely to have a substantial proportion of passive voice clauses if we want to make the Done-To our Theme, and the Doer of the action the New Information (or leave it out altogether). This pattern is typically found in various types of instructions (eg recipes) and explanations because the Done-To is usually more important than the Doer. 

For more information see:

	Text types: Explanations: Organising the information flow in explanations
	Text types: General Descriptions: Identifying and describing
	Text types: Instructions: Overview
	Text types: Recounts: Linking clauses to create a recount
	Text types: Stories: Linking clauses to create a story

Note that the terms Doer, Done-To, Subject, Theme and New Information are written with an initial capital to remind us that they are functional terms.