WordNet records no synonym and no antonym for extended care facility. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
a medical institution that provides prolonged care (as in cases of prolonged illness or rehabilitation from acute illness)
Synonyms, antonyms and the broader and narrower relations for extended care facility come from Princeton University’s WordNet. Full sources and licences.