Can the term 'that' be left out in the oppsitive clause or in the predictive clause?

I am a senior student from China. I wonder whether the term 'that' can be left out in the oppsitive clause or in the predictive clause. Grammarly speaking, 'that' can not be left out. It is necessary. However, I found that under certain circumstances 'that' could be left out in oral English through my reading some English books and newspapers. Is it an informal usage?

In formal English, it is a rule not to omit 'that' when it stands as the subject in the sub-clause.
In the case 'that' stands as an object in the sub-clause, it is more natural to omit 'that'.

JTT: I don't think it makes a difference for formal or any English, Paco. In all English, and all dialects {as far as I know} when the relative pronoun is the subject, it is never deleted.

So in your examples, Paco, #2 is never possible.

THAT =subject
(o) 1. China is the country that is growing at the fastest speed.
(x) 2. China is the country is growing at the fastest speed.

THAT= object
(o) China is the country I like to visit [...] now.
(o) China is the country that I like to visit [...] now.

JTT: Here it is optional as Paco has noted. SWE and more formal English tends to keep the relative pronoun.

By the way my dictionary says that in informal speech, nominative 'that' is occasionally left out.
There is a store on the street sells animes.
It was Romeo met Julietta.
Do you think they are not English?
I'm afraid my dictionary is more anti-prescriptive than you are.


JTT:

I'd say no, Paco. They sound strange. Perhaps in an older style of English this was the case.

What dictionary would that be?

Hello all

I don't find it that strange. Years ago there was a song that used it:

'There's a guy works down the chip shop swears he's Elvis...'

Have a good Easter break, by the way, JT.

MrP

Being a 'that-aholic', I find this thread extremely useful.
I also went to answers.com:

" That is often omitted in a relative clause when the subject of the
clause is different from the word that the clause refers to. Thus, we may
say either the book that I was reading or the book I was reading. In addition,
that is commonly omitted before other kinds of subordinate clauses, as in
I think we should try again where that would precede we. These constructions
omitting that are entirely idiomatic, even in more formal contexts."

The first clause here seems to agree with Paco. The second assertion is more
ambiguous, I would be happy if somebody gave me more examples of
those "entirely idiomatic" constructions.