The "New World" is a term often used for the majority of Earth's Western Hemisphere, specifically the Americas. The term gained prominence in the early 16th century, during Europe's Age of Discovery, shortly after the Italian explorer Amerigo Vespucci concluded that America represented a new continent, and subsequently published his findings in a pamphlet he titled Mundus Novus. This realization expanded the geographical horizon of classical European geographers, who had thought the world consisted of Africa, Europe, and Asia, collectively now referred to as the Old World, or Afro-Eurasia. The Americas were also referred to as the fourth part of the world.