əˈdɪʃən hjʊˌmæ.nɪˈtɛː.ɹɪ.ən hjuˌmæ.nəˈtɛ.ɹi.ən a component that is added to something to improve it the addition of a bathroom was a major improvement the addition of cinnamon improved the flavor someone devoted to the promotion of human welfare and to social reforms