还 and 也?

[Ferno]

Ferno' date=' compare the following (a) and (B) & their translations below:

(a) jie1 xialai yi1 ge, hai2 shi4 yi1 ge hen3 you3yong4 de, jie2gou4

The next structure, which is also a very useful one,

(B) jie1 xialai yi1 ge ye3 shi4 yi1 ge hen3 you3yong4 de jie2gou4

The next one is also a very useful structure

Please note: Your translation (=understanding) might have misled you into thinking ye3 can be used in the sentence quoted. Of couse, it can be, provided that the 2 commas are not there (with consequential change of meaning, as in my (B) sentence). Note also that (a) is only a phrase, not yet a sentence.[/quote']

:-? so if you say the phrase "which is also a very useful one", it would be gramatically incorrect to use "ye3" for "also"?

I am really confused.

Does this have something to do with the 是 verb? Or the measure word? Something else?

[HashiriKata]

I am really confused.

Yes, I think you are!

Otherwise, you should have seen clearly that "ye3" is used in expample (B), and not (a).

[Ferno]

I meant "gramatically INcorrect", sorry

[HashiriKata]

I wouldn't use the word "grammatically incorrect" ("pragmatically inappropriate", perhaps?) but in the examples, the 还 and 也 are not interchangeable:

接下来一个, 还是一个很有用的, 结构...

接下来一个也是一个很有用的结构.

[Ferno]

okay thank you... let's see if we can put some closure to this... can you tell me the grammatical rule or something that explains WHY 还是 and 也是 are not interchangable in those two sentances? So I will be able to apply it in different contexts?

Maybe "还是" is used when inserting a thought into a sentance (like the one with the commas) and 也是 is used as part of a regular, uninterrupted phrase?