The quality or state of being morally depraved, corrupt, or wicked.
From depraved (adjective) + -ness (noun-forming suffix). The -ness ending converts adjectives into abstract nouns describing qualities or states, a productive pattern in English.
Words ending in -ness are almost always abstract nouns describing inner qualities—'sadness,' 'kindness,' 'depravedness'—it's one of English's most reliable word-building tools.
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