nosologyPronunciation: /nɒˈsɒlədʒi/Definition of nosology noun [mass noun] the branch of medical science dealing with the classification of diseases. Derivatives nosologicalPronunciation: /nɒsəˈlɒdʒɪk(ə)l/ adjective nosologist noun Origin: early 18th century: from Greek nosos 'disease' + -logynosology in other Oxford dictionaries Definition of nosology in the US English dictionary