The quality or state of being curly; the degree to which something has curls or waves.
From 'curly' (adjective) plus '-ness' (noun-forming suffix creating abstract qualities), a standard formation for describing the characteristic of having curls.
The '-ness' suffix does heavy lifting in English—it lets us turn almost any adjective into an abstract noun, which is why we have words like 'happiness,' 'darkness,' and 'curliness' that capture the pure essence of a quality.
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