The passive - Thể bị động

The passive - Thể bị động 
 Active voice Passive Voice 
Present Simple 
Past Simple 
Present Perfect 
Past perfect 
Present 
Continuous 
Past Continuous 
Future Simple 
Infinitive 
Modal + be + past 
part 
He delivers letters. 
He delivered the letters. 
He has delivered the 
letters. 
He had delivered the 
letters. 
He is delivering the 
letters. 
He was delivering the 
letters. 
He will deliver the 
letters. 
He has to deliver the 
Letters are delivered. 
The letters were 
delivered. 
The letters have been 
delivered. 
The letters had been 
delivered. 
The letters are being 
delivered. 
The letters were being 
delivered. 
The letters will be 
delivered. 
letters. 
He must deliver the 
letters. 
The letters have to be 
delivered. 
The letters must be 
delivered. 
The Passive is used: 
1. When the agent (= the person who does the action) is unknown, 
unimportant or obvious from the context. 
My car was stolen. (We don't know who stole it.) 
This church was built in 1815. (unimportant agent) 
He has been arrested. (obviously by the police) 
2. To make more polite or formal statements. 
The car hasn't been cleaned. (more polite) 
(You haven't cleaned the car. - less polite) 
3. When the action is more important than the agent, as in processes, 
instructions, events, reports, headlines, news items, and advertisements. 
30 people were killed in the earthquake 
4. To put emphasis on the agent. 
The new library will be opened by the Queen. 
Changing from Active into Passive 
 The object of the active verb becomes the subject in the new sentence. 
 The active verb changes into a passive form and the subject of the active 
verb becomes the agent. The agent is introduced with by or it is omitted. 
 Subject Verb Object (agent) 
Active Picasso painted that picture. 
Passive That picture was painted by Picasso. 
 After modal verbs (will, can, must, have to, should, may, ought to) we 
use be + past participle. 
You can use the machine for cutting bread. The machine can be used for cutting 
bread. 
 We use by + agent to say who or what carries out the action. We use 
with + instrument / material / ingredient to say what the agent used. 
A cake was made by Tina. It was made with eggs, flour and sugar. 
 We put the agent (= the person who does the action) into the passive 
sentence only if it adds information. When the agent is unknown, 
unimportant or obvious it is omitted. Agents such as people (in general), 
they, somebody, etc. are omitted. 
Alexander Graham Bell invented the telephone. 
The telephone was invented by Alexander Graham Bell. (The agent is not 
omitted because it adds information.) 
Somebody pushed him. He was pushed (by somebody). (Unknown agent is 
omitted.) 
The police arrested him. He was arrested (by the police). (Obvious agent is 
omitted.)