gradualness has 2 distinct synonyms spread across 2 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is abruptness.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the property possessed by a slope that is very gradual
the quality of being gradual or of coming about by gradual stages
Synonyms, antonyms and the broader and narrower relations for gradualness come from Princeton University’s WordNet. Full sources and licences.