The sentence structure in which the logical object of a verb becomes its grammatical subject, while its logical subject is either reduced to a prepositional phrase introduced by by or removed from the sentence altogether. The subject of a passive verb is usually the person or thing that is affected by the action of the verb.
Consider the sentence They sent John to prison for five years, which is in the active voice. Its corresponding passive form is John was sent to prison for five years.
Another example is given below.
- Madame Curie discovered radium in 1898. (active voice)
- Radium was discovered (by Madame Curie) in 1898. (passive voice)
In English, the passive voice is constructed by combining the verb be with the past participle of the lexical verb.
As a rule any transitive verb can appear in the passive voice, but there are a few exceptions like have, fit, weigh and resemble.
- Ann has a nice temper. (BUT NOT A nice temper is had by Ann.)
- This suit fits you. (BUT NOT You are fitted by this suit.)
- She resembles an angel. (BUT NOT An angel is resembled by her.)
- Ann weighs 10 stone. (BUT NOT 10 stone is weighed by Ann.)
An intransitive verb cannot normally appear in the passive at all.