capability 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 incapability.
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 quality of being capable -- physically or intellectually or legally
“he worked to the limits of his capability”
the susceptibility of something to a particular treatment
“the capability of a metal to be fused”
an aptitude that may be developed
Synonyms, antonyms and the broader and narrower relations for capability come from Princeton University’s WordNet. Full sources and licences.