connects two clauses, emphasising how the following clause substantiates the preceding clause
Wiktionary
That isn't cool.
Source: Tatoeba
This isn't good.
It's not important.
This isn't money.
It's not practical.
This is not salt.
This isn't salt.
This isn't love.
It is unfair.
That isn't fair.
That's impossible.
It can't be!
It's not funny.
This is not safe.
No, it isn't possible.
This is not fish.
This is not a tiger.
This isn't a tiger.
It is not a watch.
It's not a watch.
This isn't rubber.
This is not true.
This isn't new.