(submitted by V. Suresh )

There are two things involved in the action of a transitive verb: the actor (or agent) and the thing affected by his act. Since voice pertains to action, only transitive verbs (having a 'doer' and a 'done-to') can be cast into passive voice.

Suresh constructed a strong house. This active sentence contains a transitive verb (constructed), an agent (Suresh) and a verb object (house); hence we can consider casting it into passive voice. Basically, conversion from active to passive involves (1) making the object the subject of the sentence, (2) converting the verb from 'do' to 'be done by' (in the appropriate verb form) and (3) setting the agent as the object of 'by': A strong house was constructed by Suresh

Other kinds of active sentences cannot be converted to passive forms:

Mary goes to church
. This sentence contains an intransitive verb and no object; hence this cannot be cast into passive voice.
Mary is a fine housekeeper. This sentence contains an intransitive verb and no object; hence this cannot be cast into passive voice.
Please pick up your clothing. This sentence is in imperative mood without an agent; hence this cannot be cast into passive voice.

When importance is given to the agent, the sentence and verb is usually cast in active voice: Sudhir has broken the box.
When importance is given to the thing affected by the action, the sentence and verb is usually cast in passive voice: The box has been broken by Sudhir.

Most English sentences are in active voice. When does one need to use passive voice?

· When focus is on the done rather than on the doer
· Whe the doer is not known, not clear, or is meant to be obscured or ignored.
· For impersonal expressions (scientific instructions, public announcements, notices, etc.)

Conditions underlying the change from active to passive:

· The verb must be transitive.
· Only seven tenses (simple present, present continuous, present perfect, simple past, past continuous, past perfect, simple future) can be usefully changed from active to passive voice. Constructions involving modal auxiliaries can also be changed from active to passive.

Tense Simple Present
Active Voice Devi sells dolls.
Passive Voice Dolls are sold by Devi.

Tense Present Continuous
Active Voice David is cleaning the mirror.
Passive Voice The mirror is being cleaned by David.

Tense Present Perfect
Active Voice Varun has washed the clothes.
Passive Voice The clothes have been washed by Varun.

Tense Simple Past
Active Voice Meena helped this man last Tuesday.
Passive Voice This man was helped by Meena last Tuesday

Tense Past Continuous
Active Voice Rajasekhar was teaching us dance.
Passive Voice Dance was being taught to us by Rajasekhar.
Passive Voice We were being taught dance by Rajasekhar.

Tense Past Perfect
Active Voice Renuka had paid the fees when the teacher came to class.
Passive Voice The fees had been paid by Renuka when the teacher came to class.

Tense Simple Future
Active Voice Sudhir will repair this radio tomorrow.
Passive Voice This radio will be repaired by Sudhir tomorrow.

Modal
Active Voice The police couldn't catch the robber.
Passive Voice The robber couldn't be caught by the police.

The preceding examples are to indicate the process of conversion only. In real use, passive sentences seldom contain the agent. For example, in the sentence Varun has washed the clothes, we want to indicate what Varun has done (the agent is the important point). However, if we were not concerned with the agent but instead with the accomplishment of the action, in real speech we would omit the agent: The clothes have been washed.