'that' in relative clauses

imantaghaviNow that I've seen in different contexts 'that' being replaced with all the other relative pronouns, as well.

Can you provide some examples of this?

Hi Iman,
I guess you misunderstood that sentence.
The "only" in that sentence refers to "defining clauses", so it says that you can only replace that in "defining clause" not in "indefinite clauses."
In indefinite clauses, you cannot change "that" with any other relative pronouns.
Regards
Hamid

imantaghaviCan you enlighten me about this?

Here are the basics:

Defining clauses (no comma).
(Also called restrictive clauses)

that, which, who, whom.

the book [that / which] I left in your car
the man [that / who] stopped to talk to us
the doctor [that / whom] I met last month

Thank you Hamid very much.

Iman

Hi CJ,

Thank you for your time, but my question still remains unanswered.So what you mean is 'that' can not replace all relative pronouns ( e.g: where, when)?
Because what you've mentioned is exactly what the book presents. What I want to know is whether or not 'that' can be replaced all the other relative pronouns in defining clauses.

Regards,

Iman

imantaghaviwhether or not 'that' can be replaced ...

No. where is not the same as that. when is not the same as that.

This is the house where I lived as a child. OK.
This is the house that I lived as a child. NO.

It's best to learn the use of where and when separately from the use of that,

"That" and "when" can be interchangeable, and sometimes (but not always) "where" can as well:

I remember the place that/where we stayed last year.
I haven't seen Ed since the day that/when he got married.

BillJ

Thank you CJ and BillJ very much.
As you see, both of you have different ideas from each other. And that's exactly what I want to know since I'm aware of the structure and use of the Relative Clauses except the controversial issue of using 'that' instead of 'when' and 'where'.
Any further clarification is highly appreciated in advance.

Best Regards,

Iman