[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.