I'm confused about distinguishing the meaning difference in scope of negation.
- This is a common mistake.
- This is an uncommon mistake.
I know that (1) means the mistake occurs often, and (2) means the mistake rarely occurs.
However, in these sentences,
- This is a not uncommon mistake.
- This is not an uncommon mistake.
I don't know the exact meaning in (4).
I know the negative item 'not' in (3) goes with "un" in "uncommon". Therefore, this sentence can be paraphrased as " This is somewhat common."
But, I don't get the meaning (4); however, I acknowledged that the negation scope (not) goes with "is".
Does sentence (4) have same meaning with (1)? (I just erased two negative items "not" and "un")
Or is there any other interpretation about (4)?