▪ Why do we say "no problem" instead of "not problem"? Please explain it.

Question

▪ Why do we say "no problem" instead of "not problem"? Please explain it.

Answer

because "not" is an adverb, meaning you can only use it to modify verbs and adjectives.
Since "problem" is a noun, you should use "no" which is an adjective.

Answer

You can say not a problem or no problem.     BTW, this is often used instead of saying Thanks.

Answer

No problem is short for ... it is no problem.
We often say not a problem in place of you’re welcome.

Answer

I think "no "problem is better. Because "No" problem is discribing "I don't have any problems". On the other , "Not problem "is describing "It is not a problem." ,😀