[File:Continents vide couleurs.png|thumb|300px|Color-coded map of continents: Americas North America South America Afro-Eurasia Africa Eurasia Asia Europe Antarctica Australasia/Oceania]] The boundaries between the continents of Earth are generally a matter of geographical convention. Several slightly different conventions are in use. The number of continents is most commonly considered seven but may range as low as four when the Americas and Afro-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 by convention and in practice most major islands are associated with a continent.