The quality of being reckless or lacking in care and attention.
From the obsolete adjective 'heedy' plus the noun suffix '-ness'; an archaic term that parallels the more common 'heedlessness.'
English had multiple ways to describe being careless—'heediness,' 'heedlessness,' 'thoughtlessness'—but over time we keep just one or two versions and the others fade away.
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