flexibility has 3 distinct synonyms spread across 3 of its 3 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 inflexibility.
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 of being flexible; easily bent or shaped
the quality of being adaptable or variable
“he enjoyed the flexibility of his working arrangement”
Synonyms, antonyms and the broader and narrower relations for flexibility come from Princeton University’s WordNet. Full sources and licences.