North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere.
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent.
Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere.
Asia is Earth's largest and most populous continent, located primarily in the Eastern and Northern Hemispheres.
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km².