We change a sentence from active to passive when we want to emphasise the action rather than the doer. The object of the active sentence becomes the subject of the passive.
Form
Subject + be (in the right tense) + past participle. The original subject becomes 'by + agent' (often omitted).
- Active: The mayor opened the conference.
- Passive: The conference was opened by the mayor.
Why use the passive
When we change an active to a passive sentence, the active object becomes the subject of the passive — and the focus changes to the action / receiver.
Tenses in the passive
Present: am/is/are + V3. Past: was/were + V3. Present perfect: has/have been + V3. Future: will be + V3. Modal: modal + be + V3.
- The project will be finished by next week.
- The workshop and café equipment hasn't been set up yet / will be finished.
Common exam trap
When the doer is unknown or obvious, we drop 'by ...'. 'A famous pirate' → Silver's parrot was named after a famous pirate.