The state or quality of being diseased; the condition of suffering from illness or corruption.
From diseased + -ness (noun suffix indicating state or condition). Common in Middle English medical and philosophical texts to describe both physical and moral sickness.
Medieval physicians wrote about the 'diseasedness of the humours'—they literally believed disease was an imbalance of four liquids in your body, so 'diseasedness' was a measurable, describable property they tried to correct with bloodletting.
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