The quality or state of being buoyant, either literally (able to float) or figuratively (cheerful and optimistic).
From buoyant + -ness (a noun suffix creating abstract nouns). The -ness suffix directly attaches to adjectives to form nouns describing their qualities.
While 'buoyancy' is the technical term, 'buoyantness' appears in older texts and poetry, emphasizing the quality itself—the British especially favored -ness formations, which is why older literature has more buoyantness than modern scientific writing.
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