The quality or state of being diabolic; extreme wickedness or evilness.
Formed by adding the -ness suffix to diabolical (the adjective form of diabolic), a standard English nominalizing pattern that transforms descriptive words into abstract nouns.
English's -ness suffix is incredibly powerful—you can add it to almost any adjective to create a noun expressing that quality, making it one of the most flexible tools for creating new words.
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