The quality or state of being celestial; heavenly character or divine nature.
From 'celestial' plus the suffix '-ness' (meaning state or quality). This formation represents a traditional English way of converting adjectives into abstract nouns to express essential qualities.
Celestialness and celestiality mean almost the same thing, but celestialness sounds homier and more natural—it's what happens when English takes a Latinate adjective and makes it genuinely English-feeling by adding '-ness' instead of '-ity'.
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