it's not/it isn't

[khess6669]

Sophie wrote:

Is there any difference in tone and or usage between saying "it's
not" and "it isn't"?
 
Paula wrote:
 
For example, from childhood always remembered kids on the playground 
yelling, "It's not, either!"  But the teacher would say, "It isn't 
correct, polite, etc."


==
KB here:

Reference to the schoolyard makes me think of one distinction between 
them. Kids sometimes enjoy the following pun:

- It is.
- No, it's SNOT!

Sounds pretty much the same when you say it out loud, but they're 
really saying "No, it is nose mucus." (You can't make that childish 
joke if you say, politely, "No, it isn't.")

Sorry to take this from PhD linguists to schoolyard silliness, but I 
thought it was worth a mention.

KB