The quality or state of being ceremonial; the degree to which something adheres to formal rituals and traditional procedures.
From 'ceremonial' (adjective) plus the noun-forming suffix '-ness', which creates abstract nouns describing qualities. This pattern allows any adjective to become a countable quality.
The suffix '-ness' is one of English's most productive tools—you can slap it onto almost any adjective to create an abstract noun, which is why we get ceremonialness even though it's rarely used; this demonstrates how English's grammar rules are more powerful than actual usage.
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