Eg. First one is:
The room should have cleaned.
And the second one is:
The room should have been cleaned.
What is the difference in terms of their meaning?
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Let's simplify this and remove the should have from both examples.
The room cleaned ...
The room was cleaned ...
The second example is a passive voice construction - form of to be + past participle form of verb. This is fine.
The first example is wrong because rooms don't normally clean anything. People clean rooms.
If we don't know who cleaned the room, but know it didn't clean itself magically, that's a perfect case for passive voice and one of the reasons it's used.
Passive voice works with modals like non-passively expressed verbs.
The room is cleaned.
The room must be cleaned.
The room has been cleaned.
The room would have been cleaned.
Another use of the passive voice: When people or an entity does not want to take responsibility for something
Politicians and bosses will use the passive voice:
"Mistakes were made" vs "I made a mistake." or "We made a mistake."
Here, the passive voice was a way to avoid saying...
"The housekeeper should have cleaned the room" (use "should have" in the active)
The room should have BEEN cleaned. (add BEEN to the passive)