ok I believe that I understand this.
for example:
The boy, which we saw him on the train, is standing over there.
The man, that his dog have been barkink all night, had agreed to take better control to take better control of his animals.
Hi Shaolinone,
I'm afraid you don't have it right:-

-(. Let me try to help you;-);-). Unless I'm much mistaken your question is about relative clauses and the use of the relative pronouns 'that' and 'which'.
1) These relative sentences give the same kind of information about a noun as adjectives do, they help us to define that item in more detail: 'A man' but 'A tall man' -gives more information- and 'The tall man that came with a bag' -gives even more-, and 'The tall man that came with the bag that was full of magazines' -gives much more-. In this kind of relative clause you can use both 'who' (more formal) or 'that' as pronouns to connect the information you want to give with the noun you want to DEFINE by using a clause -a clause consists of, at least, subject and verb-. Sometimes the clause you use has its own subject -different from the noun you are defining- and then you can leave 'who' or 'that' out; as in 'The tall man (who/that) I met yesterday'. On some other ocassions the subject of that clause you want to use to define a noun is the same as the noun you are defining, and then you need 'who' or 'that', as in: The tall man who came yesterday. We call this kind 'DEFINING RELATIVE CLAUSES' because the information helps the speaker/writer to define that noun or noun group.
Ok, so far, then take a deep breath, write your own examples, and go on reading;-):
2) When the noun we are defining is not a person or group of people we can use 'which' (formal) or 'that' to connect the clause to the noun. Thus, OK, if you use 'that' they will always be fine. Again, write your own examples;-).
3) Don't forget that 'who', 'that' or 'which' in these sentences are pronouns. This means that we use them not to repeat a noun. Look at this:
The tall man that I phoned THE TALL MAN yesterday--> it is not OK because here 'that' and 'THE TALL MAN' are the same person (The man is tall. I phoned the tall man). OK, the same happens when you use 'him' instead of 'the tall man'--> 'The tall man that I phoned HIM yesterday' is not ok. Remember that you have 'THAT' meaning 'him' here so 'The tall man that I phoned yesterday' is ok. And still better, the information you give about this 'tall man' is the clause 'I phoned him'. This clause has its own subject 'I' that is different from 'the tall man' so we can say 'The tall man I phoned yesterday' and is ok.
Stand up, have a glass of water, write your own examples and go on reading;-).
4) Again, a sentence like 'The old chair which/that the old chair was next to the window' is not ok because here 'which/that' and 'the old chair' are the same thing. The correct one is 'The old chair which/that was next to the window'. And here you have to keep 'which' or 'that' because the clause you use to define that chair is 'the old chair was next to the window' and the subject in this clause has a subject 'the old chair' and it is the same as the noun you are defining. Ok, write some more examples, we are almost finished:lol:.
5) Sometimes you want to define a noun that needs no more information to be defined because it is already very well-defined. For example, 'George W. Bush'. Then we don't say 'George W. Bush that phoned yesterday lives in Washington', it is grammatically perfect but there is no need to give more information about that person to know who we are talking about. If we want we can say something extra, additional about him but what we say will not help us to define it. This are NON-DEFINING relative clauses and the extra information we give goes between commas (, ... ,). For them we need relative pronouns too, but only WHO for people and WHICH for the rest -there are some more but I think that's enough for today- and we can form sentences like, 'George W. Bush, who loves animals, lives in Washington'. In this non-defining you can't leave 'who' or 'which' out. And this is true not only for George W. Bush but also for Peter's father -even if you don't know Peter-, The Manager of Harrods, Tony or my sister's dog. They are all well-defined names and noun groups so we can't define them any further and the information we give about them is extra, additional, and goes between commas with who or which as a relative PRONOUNS. Write your own examples and let's finish:lol::lol::lol::
6) Here, again, remember they are pronouns so don't repeat the noun;-).
Thus, your examples should be:
The boy (who/that) we saw on the train is standing over there
The man WHOSE dog had been barking all night long agreed to control his animals better.
and further examples are:
My mother's neighbour, who can be exasperating, is coming for dinner.
The neighbour that we usually meet in the supermarket is pregnant again.
A dog that a lorry had run over helped to rescue a lost climber.
James's dog, which is as big as an armchair, ate his mobile phone.
If you have read this far and have understood half of it I will be more than happy. However, I do warn you I'm not a teacher.:-D:-D:-D
Bye.