The quality or state of being inclined to complain; the characteristic of expressing dissatisfaction frequently.
From 'complaining' (present participle of 'complain') + '-ness' (Old English suffix forming abstract nouns). This double nominalization (complain → complaining → complainingness) shows how English builds abstract concepts through suffixation.
Adding '-ness' to adjectives or participles is how English speakers create abstract nouns, but words like 'complainingness' are relatively rare because we usually just say 'complaining' or use other forms—the '-ness' version feels unnecessarily formal.
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