Interested in Language
"He has not shown an improvement at all..."
"He has not shown improvement at all..."
I am sure the first sentence is incorrect and the second is correct.
Please tell me if my explanation is as well right - Improvement is an adverb in this context, and adverbs are not countable as it describes/modifies the function of the verb.
Improvement is a noun, not an adverb.
The first sentence is better than the second.
Better still would be "He has not shown any improvement at all."
End the sentence with a full stop. There's no need for an ellipsis there.
A better title would have been He has not shown an improvement at all.