A "one-hit wonder" is an act that appears on the chart just once. The term "true one-hit wonder" was the term given by Guinness Book of British Hit Singles & Albums (and also the Billboard book Top Pop Singles) is an act that has one number one hit and nothing else on the chart ever. If an act appears in some other form, (for example) a solo act that appears with a band or with other acts then these are taken separately.