of verb is an aspect that tells whether the subject is the doer or the receiver of the action. It can be active or passive.
When the subject is the doer of the action (verb), the voice of verb is active.
To make an active voice:
Subject + main verb
example: He passed the test.
In this sentence, the subject He did the action which was passing the test.
The verb is in passive voice when the subject receives the action.
To make a passive voice:
Subject + auxiliary verb (to be) + main verb (past participle*)
example: The test was passed by him.
In this sentence, the subject test did not do the action. It was “him” who did. The subject “test” receives the action done by him.
Uses of passive voice
Passive voice is used to:
1. Give importance to the object.
Rather than saying: Aldrin won the presidency; we say:
The presidency was won by Aldrin. (presidency is given more importance)
2. When the doer is unknown.
Aldrin was asked to run. (It is unknown who asked Aldrin to run)
Changing Voice of Verb
It is simple to change active to passive and vice versa.
To change active to passive, simply make the subject in the active voice the object of the sentence in the passive voice introduced by the preposition “by”.
To change passive to active, simply make the object of the preposition (the word after by) the subject of the sentence.
Please note though that when changing voice, the verb must agree in number with the subject, and the tense (time) must be the same as the tense in the original sentence.
Active: (1) The military rescued the victims.
Passive: (1) The victims were rescued by the military.
Passive: (2) A fundraising activity was organized by him.
Active: (2) He organized a fund raising activity.
Active: (3) The victims thanked the military.
Passive: (3) The military were thanked by the victims.
In sentence 1(passive voice), were rescued is in simple past tense because the tense in the active voice is also simple past tense and “were” was used because the subject “victims” is plural. In sentence 2, organized was used in the active voice because the verb “was organized” in the passive voice is in simple past as well. In sentence 3, the subject military is a collective noun taken as individuals (members of the military), so plural verb “were thanked” was used in the passive voice.
The same rule also applies in perfect tenses like these sentences below:
Active: (1) Eleanor has just won the contest. (present perfect)
Passive: (1) The contest has just been won by Eleanor.
Passive: (2) They have been given reprieve by the court.
Active: (2) The court has given them reprieve.
Notice that in the second sentence, there was a change in the number of verb. The passive voice used “have been given” while the active voice used “has given.” The shift happened because of the change in number of the subject. They is plural while court is singular, thus the change in number.
Knowledge of changing voice of verb is so important in writing especially if you want to achieve consistency and parallelism in your writing.
Consistency of Voice:
Incorrect: I ran to the car very quickly, but soon found out that the car key was left in the house by me. (active and passive)
Correct: I ran to the car very quickly, but soon found out that I left the car key in the house. (active and active)
* Past participle is not the same as past tense. Verbs in past participle are normally used after an auxiliary verb/be verb like in pasive voice. You can't distinguish a past participle from past tense if the verb is a regular verb (ending in -d or -ed) unless the verb is used in context. However, if a verb is irregular (different spelling), past participle is distinguishable.
wash (present), washed (past tense), washed (past participle)
He washed his uniform. (past tense)
His uniform was washed by him. (past participle)
write (present tense), wrote (past tense), written (past participle)
He wrote the essay. (past tense)
The essay was written by him. (past participle).
Try to familiarize the conjugation of verbs so as not to commit silly mistakes.