Passive voice

1. Passive voice is used when the focus is on the action. It is not important or not known, however, who or what is performing the action.
Example: My bike was stolen.

In the example above, the focus is on the fact that my bike was stolen. I do not know, however, who did it.

Sometimes a statement in passive is more polite than active voice, as the following example shows:

Example: A mistake was made.

In this case, I focus on the fact that a mistake was made, but I do not blame anyone (e.g. You have made a mistake.).
Form of Passive

Subject + finite form of to be + Past Participle (3rd column of irregular verbs)

Example: A letter was written.

When rewriting active sentences in passive voice, note the following:
the object of the active sentence becomes the subject of the passive sentence
the finite form of the verb is changed (to be + past participle)
the subject of the active sentence becomes the object of the passive sentence (or is dropped)
Examples of Passive Level: lower intermediateTense Subject Verb Object
Simple Present Active: Nina writes a letter.
Passive: A letter is written by Nina.
Simple Past Active: Nina wrote a letter.
Passive: A letter was written by Nina.
Present Perfect Active: Nina has written a letter.
Passive: A letter has been written by Nina.
Future I Active: Nina will write a letter.
Passive: A letter will be written by Nina.
Hilfsverben Active: Nina can write a letter.
Passive: A letter can be written by Nina.

Examples of Passive Level: upper intermediateTense Subject Verb Object
Present Progressive Active: Nina is writing a letter.
Passive: A letter is being written by Nina.
Past Progressive Active: Nina was writing a letter.
Passive: A letter was being written by Nina.
Past Perfect Active: Nina had written a letter.
Passive: A letter had been written by Nina.
Future II Active: Nina will have written a letter.
Passive: A letter will have been written by Nina .
Conditional I Active: Nina would write a letter.
Passive: A letter would be written by Nina.
Conditional II Active: Nina would have written a letter.
Passive: A letter would have been written by Nina.

Passive Sentences with Two Objects Level: intermediate

Rewriting an active sentence with two objects in passive voice means that one of the two objects becomes the subject, the other one remains an object. Which object to transform into a subject depends on what you want to put the focus on. Subject Verb Object 1 Object 2
Active: Nina wrote a letter to me.
Passive: A letter was written to me by Nina.
Passive: I was written a letter by Nina.