Voice tells whether a subject is acting (He questions us) or being acted upon (He is questioned). When the subject is acting, the verb is in the active voice; when the subject is being acted upon, the verb is in the passive voice. Most contemporary writers use the active voice as much as possible because it makes their prose stronger and livelier. To shift a sentence from passive to active voice, make the performer of the action the subject of the sentence.

Use the passive voice when you want to emphasize the recipient of an action rather than the performer of the action.

Colonel Muammar al-Qaddafi was killed during an uprising in his hometown of Surt.

In scientific and technical writing, use the passive voice to focus attention on what is being studied.

The volunteers’ food intake was closely monitored.