The quality or state of being agonizing; the degree to which something causes extreme pain or distress.
From 'agonizing' (present participle of 'agonize') + '-ness' (suffix forming abstract nouns). The '-ness' suffix converts adjectives into nouns representing the quality or state they describe.
This word is rarely used because English speakers prefer shorter words like 'agony' or 'anguish,' but it perfectly demonstrates how English lets you turn almost any adjective into an abstract noun with '-ness'—a tool that lets us describe the 'ness' of nearly anything!
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