what usage in between sentence

[rte.sushil]

post207.html#p207

Ignoring the other problems with this choice, we're trying to link a dependent clause to the main sentence; for that, we use relative pronouns. This sentence would have to say something like "recession, which many had feared..." "Which" is a relative pronoun, "what" is not ("what" can be either an interrogative pronoun or an interrogative adjective - generally used for asking questions).

These two are often used interchangeably (but incorrectly) in spoken English and so many of us have lost our ability to "hear" the incorrect usage of "what" when we should be using "which."

_________________
Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT

i understand that which is a relative pronoun and what is not.
But i am not able to express in words when to use what in the sentence.

such as :-
A leading figure in the Scottish Enlightenment,Adam Smith wrote two major books that are to democratic capitalism what Marx’s Das Kapital is to socialism

here what is used to clarify for comparison.

are there some rules that can help to identify when can we use "what" in sentences in places other than interrogative pronoun (what happened/what do you know?)or an interrogative adjective (what things you don't know)?

[RonPurewal]

OG problems are banned on this forum. Please don't link to an OG thread in an attempt to continue discussing it.

Thanks.