First I'm kinda confused. I'm concerned if these 2 questions bring the same
nuance or not... "Isn't he young?" and "He is not young? / He isn't young?".
Both sounds quite different on how they imply the speaker's perspective.

I believe that these 2 questions are different...

> 彼は医者じゃない? 彼は医者なんじゃない?
>
> 授業がない? 授業があるんじゃない?

The former just asked "He is not a doctor?" and "There is no class?", which
imply that the speaker wanted to clarify the negative situation.

The latter is explanatory seeking. "Isn't he a doctor? (I thought he is!)" and
"Isn't there a class? (I thought there is!)" imply that the speaker wanted to
clarify that their first stimuli received are wrong.

Here comes い adj.

> 臭くない?

Here the guy is asking "Isn't it Smelly? (It's stinky!)", more like "It's
stinky, right? (asking for the listener's agreement).

> 怖くないの?

this is translated as "you aren't scared?"

and furthermore if I add の after じゃない, what changes?

> 授業があるんじゃない vs 授業があるんじゃないの

does the latter just mean more explanatory seeking?

The whole ordeal confuses me. **If indeed those 2 questions at the beginning
differ** , can someone explain to me every formula in constructing negative
questions with/without の that gives out specific nuances?
CC BY-SA 3.0
2017-06-23T10:53:59.607
48681
2017-06-24T20:38:29.540
2020-06-17T08:18:27.500
-1
15891
question
grammar questions no-da
Negative questions + の
The の particle here is the explanation particle, it gives an emphasis and
further wish of explaining from the person who answers, I think it makes the
question a bit stronger cause you just don't want an answer, you want a proper
explanation.

> パーティーに行かない？（Paatii ni ikanai?) Are you not going to the party?
>
> パーティーに行かないの？（Paatii ni ikanai no?) Are you not going the party? (explain to
> me why)

You can also abbreviate の with ん, for instance:

> 彼女が好きじゃないんだ？(Kanojo ga suki janain da?) Don't you like her? (why)

Now, I'm not 100% sure when it comes to questions, but for affirmatives when I
use んだ, なんだよ people often say to me that it makes the sentence too strong, and
it doesn't always fit. Something like.

> 今日、大学に行かないんだよ (kyou, daigaku ni ikanain da yo) I'm not going to college
> today!!!
CC BY-SA 3.0
2017-06-23T12:46:08.117
48682
2017-06-23T14:11:21.103
2020-06-17T08:18:27.500
-1
16104
48681
answer
Correct me if I'm wrong but の is an informal way of using か, I mean as a
question, instead of using ですか or か you can use の, also when you can use it in
a negative way: adjないの? It means aren't you (hungry,scared,etc).

I would say that the meaning depends of the context, like many things in
japanese, also If is a conversation you have to pay attention to the
intonation to get what the speaker is trying to communicate.
CC BY-SA 3.0
2017-06-23T14:22:37.197
48686
2017-06-23T14:22:37.197
20261
48681
answer
Questions of のだ forms mean that you are trying to confirm if your judgement
from your observation is true or not, opposed to simple questions.

For example, simple くれる？ means that your are asking someone to give something
while くれるの？ means that the opponent seems giving it and you are confirming if
he's really doing.

Negative questions are basically parallel too. 怖くないの？ means that you first
caught a sign that told the opponent was not scared. That part is the
difference.

As for your examples, both 彼は医者じゃない? and 彼は医者なんじゃない? can mean either that you
are guessing that he is a doctor or that you are surprised at the fact that he
is not a doctor. This is because if he's doctor or not is a permanent state
unlike if someone is scared at the moment. The examples of 授業 are parallel
too. So, 授業があるんじゃない? is not different from 授業があるんじゃないの? either.
CC BY-SA 3.0
2017-06-24T20:38:29.540
48716
2017-06-24T20:38:29.540
4092
48681
answer