High Quality Content by WIKIPEDIA articles! The borders or boundaries separating the various continents of the topography of Earth are a matter of geographical convention. Several slightly different conventions are in use, just as the number of continents is most commonly considered to be seven but may range as low as five, depending on whether the Americas and Eurasia are each considered a single continent. According to the definition of a continent in the strict sense, an island cannot be part of any continent, but in practice most major islands are associated with a continent by convention.