The quality or state of being autumnal; the characteristic nature or essence of autumn.
From autumnal + -ity (suffix forming abstract nouns). A rare, poetic formation from the 19th century attempting to capture the abstract essence of autumn.
'Autumnity' is so obscure that it barely exists in modern English, but when writers do use it, they're reaching for something deeper than just 'autumn'—the philosophical feeling of seasonal decline.
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