In the active voice the subject does the action. In the passive voice the subject receives the action.
Active: The chef cooked the meal.
Passive: The meal was cooked by the chef.
How to form the passive
Use to be (in the right tense) + the past participle: is made, was built, will be written, has been finished.
When to use the passive
- The doer is unknown or unimportant: “The window was broken.”
- The result matters more than the doer: “The bridge was built in 1990.”
In most everyday writing the active voice is clearer and shorter.