Dwipa (Sk.). An island or a continent. The Hindus have seven (Sapta dwipa ); the Buddhists only four. This is owing to a misunderstood reference of the Lord Buddha who, using the term metaphorically, applied the word dwipa to the races of men. The four Root-races which preceded our fifth, were compared by Siddhârtha to four continents or isles which studded the ocean of birth and death—Samsâra.
Source: H.P.Blavatsky - The Theosophical Glossary