what is the way to distinguish between the following:
nothing, anything, something?
This is a question that cannot be answered so simply; much depends on context.
'Nothing' is the universal singular negative indefinite nonpersonal countable compound pronoun.
'Anything' is the partitive singular non-assertive nonpersonal countable compound pronoun.
'Something' is the partitive singular assertive nonpersonal countable compound pronoun.
There is nothing wrong.
There isn't anything wrong.
There is something wrong.
Nothing is wrong.
Something is wrong.
Is (n't) something wrong?
Is (n't) anything wrong?
Is nothing wrong?
I think that pretty much covers it.