abnormality has 4 distinct synonyms spread across 4 of its 4 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 normality.
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.
an abnormal physical condition resulting from defective genes or developmental deficiencies
Synonyms, antonyms and the broader and narrower relations for abnormality come from Princeton University’s WordNet. Full sources and licences.
retardation sufficient to fall outside the normal range of intelligence
marked strangeness as a consequence of being abnormal
behavior that breaches the rule or etiquette or custom or morality