enerally divided into several, large, discrete
landmasses termed continents. Depending on the convention used, the
number of continents can vary from five to seven. The most common
classification recognizes seven, which are (from largest to
smallest): Asia, Africa, North America, South America, Antarctica,
Europe, and Australia. Asia and Europe are sometimes lumped together
into a Eurasian continent resulting in six continents.
Alternatively, North and South America are sometimes grouped as
simply the Americas, resulting in a continent total of six (or five,
if the Eurasia designation is used).
North America is commonly understood to include the island of
Greenland, the isles of the Caribbean, and to extend south all the
way to the Isthmus of Panama. The easternmost extent of Europe is
generally defined as being the Ural Mountains and the Ural River; on
the southeast the Caspian Sea; and on the south the Caucasus
Mountains, the Black Sea, and the Mediterranean. Africa's northeast
extremity is frequently delimited at the Isthmus of Suez, but for
geopolitical purposes, the Egyptian Sinai Peninsula is often
included as part of Africa. Asia usually incorporates all the
islands of the Philippines, Malaysia, and Indonesia. The islands of
the Pacific are often lumped with Australia into a "land mass"
termed Oceania or Australasia.
Although the above groupings are the most common, different
continental dispositions are recognized or taught in certain parts
of the world, with some arrangements more heavily based on cultural
spheres rather than physical geographic considerations.

Map references:

Physical Map of the World, Political Map of the World, Standard Time
Zones of the World

Area:

total: 510.072 million sq km
land: 148.94 million sq km
water: 361.132 million sq km
note: 70.9% of the world's surface is water, 29.1% is land

Area - comparative:

land area about 16 times the size of the US

Land boundaries:

the land boundaries in the world total 251,060 km (not counting
shared boundaries twice); two nations, China and Russia, each border
14 other countries
note: 45 nations and other areas are landlocked, these include:
Afghanistan, Andorra, Armenia, Austria, Azerbaijan, Belarus, Bhutan,
Bolivia, Botswana, Burkina Faso, Burundi, Central African Republic,
Chad, Czech Republic, Ethiopia, Holy See (Vatican City), Hungary,
Kazakhstan, Kosovo, Kyrgyzstan, Laos, Lesotho, Liechtenstein,
Luxembourg, Macedo