ability has 1 distinct synonym spread across 1 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 inability.
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 able to perform; a quality that permits or facilitates achievement or accomplishment
possession of the qualities (especially mental qualities) required to do something or get something done
“danger heightened his powers of discrimination”
Synonyms, antonyms and the broader and narrower relations for ability come from Princeton University’s WordNet. Full sources and licences.