adept [adepts](one fully skilled or well versed in anything) noun [UK: ˈæ.dept] [US: ə.ˈdept]
contributor [contributors](a person who backs, supports or champions a cause, activity or institution) noun [UK: kən.ˈtrɪ.bjuː.tə(r)] [US: kən.ˈtrɪ.bjə.tər]