The word "continent" comes from the term "continent land", translated from the Latin terra continens and meaning "continuous land" and defines one of several landmasses on Earth.
This definition suggests only four continents as the Americas (made up of South and North America), Afro-Eurasia (made up of Africa, Europe and Asia), Antarctica and Oceania all provide continuous landmasses. However, the more common definition divides the aforementioned into seven separate regions not necessarily separated by water, which we refer to as the continents.
The Americas are divided along the Colombia-Panama border, while Antarctica is it's own continuous landmass and Oceania is made up of the Australian landmass and Pacific islands, including New Zealand. Europe's eastern border with Asia is usually given as the Ural Mountains, Caspian Sea, Caucasus Mountains, the Black Sea and the waterways connecting each, which Asia is separated from Africa along the Suez Canal.
The largest continent Asia sits directly to the north and is more than four times the size of the smallest, Australia. Asia is also the most densely populated with over 4 billion people, equating to 60% of our planet's population, inhabiting it. Not wanting to be outdone on anything, Asia also has the world's tallest point, Mount Everest at 8,848 metres, and lowest point, the Dead Sea at -422 metres.
In geological terms the continents are described using the tectonic plates, which move, collide and divide, providing an ever-changing mosaic on the surface of the Earth, also known as "continental drift". The tectonic plates are composed of oceanic or continental lithosphere, topped by an outer crust. The movement of the Earth's core slide the tectonic plates against or along each other, with subduction carrying plates back into the liquid mantle or throwing up mountain ranges.
Originally starting as the supercontinent Pangaea, the tectonic plates have slowly moved into the arrangement we see today leaving fossil evidence along its previous boundaries, such as related plant and animal life found in both South America and Africa which have been separated by hundreds of miles of Ocean for millions of years.