The passive voice

The passive puts the object first: be in the right tense plus the past participle: the letter was sent, the bridge is being built, the results will be published. Add by for who did it: written by a student.

Use it when the doer is unknown, obvious or less important than the action: my bike was stolen, English is spoken here.

The participle never changes, but be agrees with the subject: the house was sold, the houses were sold. Irregular participles must be known: written, built, taken, chosen.