Conjunctions, dependent and independent clauses

Question

I have a question about conjunctions, dependent and independent clauses.

The issue came up when a text book suggests that "and it" can replace "which/who". But my understanding is that subordinating conjunctions are used for connecting dependent clauses, whilst coordinating conjunctions are used with independent clauses.

So here are some examples.

This book is about King Sejong, who invented Hangeul. This book is about King Sejong and he invented Hangeul. No.1 to me is correct whilst 2. isn't.

Another example however

The word shampoo comes from the Hindi word champo, which means "to press". The word shampoo comes from the Hindi word champo and it means "to press". In this case, both look correct to me.

In the 1st example, is it incorrect because the subordinate clause acts as a adjective clause, whilst the 2nd example isn't?

One final example that is obviously wrong:

I am reading a book about Paris, which I visited two years ago. I am reading a book about Paris and I visited two years ago.

I tried asking on English Stack Exchange but only received one comment saying

"The whole point of having relative clauses is to avoid having to use your examples with "and""

But no clear explanation on the exact grammar at play which allows some cases to be okay whilst in others, not.

Is there a grammar mistake in the wrong sentences? Or is it just semantically unclear?

Thank you.

Answer 1

The idea of replacing ", which" with ", and it" is not strict equivalence, but a a general similar meaning. The intention is to demonstrate to the student how a non-restrictive clause adds additional information. This additional information could often be added in a co-ordinated clause or even in a separate sentence.

So the first example "This book is about King Sejong, who invented Hangeul." could be roughly expressed as

This book is about King Sejong. Did you know that King Sejong invented Hangeul?

Obviously the first way of saying it is shorter and clearer, and it doesn't have a rhetorical question, but the meaning is roughly the same. Using "and he" is not good English. We would usually use a relative clause, and only use "and" to list other things that the book is about. So it's correct, but only useful to illustrate that the relative cluase exists only to give extra information, not to identify a particular king.

The second one is also unclear with "and": Does "shampoo" or "champo" mean "to press? (of course in context the answer is clear, which is why you have no problem understanding).

Not sure why you say the last example is "obviously wrong". It is certainly better to use the relative clause, but the and expression is just odd, not really wrong, again I think because when we hear "and" we expect a second thing that the book is about.

So the idea of changing ", which" to ", and it" is not that you should do it, but to understand the difference between a restrictive and non-restrictive clause. Once you understand it, you can forget about changing "which" to "and".