There isn’t anybody in the room.
There isn’t anyone in the room.
There is nobody in the room.
There is no one in the room.
A: Who is in the room?
B: Nobody. / No one.
There isn’t anything in the bag.
There is nothing in the bag.
A: What’s in the bag?
I don’t know anybody (or anyone) here.
I’m lonely. I have nobody to talk to. (= I don’t have anybody)
The house is empty. There is no one in it. (= There isn’t anyone in it.)
I can’t remember anything.
She said nothing (= She didn’t say anything)
There’s nothing to eat (= There isn’t anything to eat)
The house is empty. Nobody lives there.
-Who did you speak to?
-What did you say?
He doesn’t know anything (not He doesn’t know nothing)
Don’t tell anybody. (not Don’t tell nobody)
There is nothing to do in this town. (not There isn’t nothing)