The quality or state of being extremely delicious; the pleasantness of taste or appeal that makes something delightful.
From delicious (Latin deliciosus) plus the abstract noun suffix -ness, which transforms adjectives into nouns describing qualities or conditions.
The suffix -ness is one of English's most productive word-building tools, allowing us to convert almost any adjective into an abstract noun—deliciousness is so satisfying to say that it's become common in casual speech and food writing.
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