Passive Voice

The passive voice is a grammatical construction (a "voice") in which the subject of a sentence or clause denotes the recipient of the action (the patient) rather than the performer (the agent). In the English language, the English passive voice is formed with an auxiliary verb (usually be or get) plus a participle (usually the past participle) of a transitive verb.

A sentence featuring the passive voice is sometimes called a passive sentence, and a verb phrase in passive voice is sometimes called a passive verb. English differs from languages in which voice is indicated through a simple inflection, since the English passive is periphrastic, composed of an auxiliary verb plus the past participle of the transitive verb.

A passive voice is form by Subject + to be + Past Particle / Verb3. Usually only a transitive verb can be changed from active voice to passive voice. Passive voice is used as the object of the active voice is more important information than its subject.

To change a sentence from active to passive voice, do the following:

1. Move the active sentence's direct object into the sentence's subject slot

2. Place the active sentence's subject into a phrase beginning with the preposition by

3. Add a form of the auxiliary verb be to the main verb and change the main verb's form

Because passive voice sentences necessarily add words and change the normal doer-action-receiver of action direction, they may make the reader work harder to understand the intended meaning.

As the examples below illustrate, a sentence in active voice flows more smoothly and is easier to understand than the same sentence in passive voice.

It is generally preferable to use the ACTIVE voice.

To change a passive voice sentence into an active voice sentence, simply reverse the steps shown above.

1. Move the passive sentence's subject into the active sentence's direct object slot

2. Remove the auxiliary verb be from the main verb and change main verb's form if needed

3. Place the passive sentence's object of the preposition by into the subject slot.

Because it is more direct, most writers prefer to use the active voice whenever possible.

The passive voice may be a better choice, however, when

• the doer of the action is unknown, unwanted, or unneeded in the sentence

Examples

• the writer wishes to emphasize the action of the sentence rather than the doer of the action

Examples

• the writer wishes to use passive voice for sentence variety.

Example : The thread is posted.
The letter was burned.
The city was founded by Eric Gargaton.
Jungle has been converted into forestry.
Caesar was stabbed by Brutus.

Sumber : http://www.towson.edu/ows/activepass.htm
http://swarabhaskara.com/miscellaneous/active-and-passive-voice/
http://en.wikipedia.org/wiki/English_passive_voice