The Western World, also referred to as simply the West, is a term that can mean different things depending upon the speaker and the context. It is sometimes used incorrectly as a synonym for countries in the Western Hemisphere or even for just Western Europe on its own. However, its true meaning is somewhat more nuanced.
The most widely accepted modern definition of the "Western World" is based not upon geographical location but upon the cultural (or when appropriate, political or economic) identities of the countries in question. Using this definition, the Western World includes Europe as well as any countries whose cultures are strongly influenced by European values or whose populations include many people descended from European colonists—for example Australia, New Zealand, and most countries in North and South America (see "The modern meaning of the Western World (the Latin West)" below).
The concept of the "Western World" originated in the actions of the Roman emperor Diocletian, who chose in 285-286 CE to divide his empire into two halves, each with its own separate capital, government, and church. On one side was what we now call the Western Roman Empire, also known as the Occident (Latin for "sunset" or "western"), which included Italy and the European and African countries west of it. On the other side was the Eastern Roman Empire, or Orient (Latin for "rise" or "east"), which encompassed Greece, Egypt, and the regions that are now Turkey, Syria, Israel, and other Middle Eastern countries. Roughly a century later (410-476 CE), the West Roman Empire collapsed, but the East Roman Empire would last another 1000 years (and later be renamed the Byzantine Empire), until conquered by the Ottomans in 1453.
These differing conditions led to tension between the Roman Catholic Church, which served the former Western Roman Empire, and the Eastern Orthodox Church, which served the Eastern Roman empire. Making matter worse was a pervasive cultural belief, inspired by a claim from the ancient Greek historian Herodotus that the Greeks defeated the Persians in 480-479 BCE because "free people fight better than slaves", that the people of the west were somehow more noble or free than those of the east.
This animosity deepened the political and cultural rift between the two sides and helped propagate and reinforce the notion that the two sides were plainly different. Thus, the "Western World" became the western portion of Europe (up to Italy) and the East came to mean Eastern Europe, Asia and all its subregions: The Middle East, South Asia, Southeast Asia, North Africa, and the Far East.
However, this original definition is virtually extinct today—in fact, it is painfully inadequate, given that it fails to include new Western World countries such as Australia and New Zealand (both "Western" countries that are geographically located in the Eastern Hemisphere) and all of North and South America.
The culture of the Western World evolved quickly after the collapse of the West Roman Empire, influenced by the traditions of the Renaissance, the Protestant Reformation, and the Age of Enlightenment. Furthermore, when the Ottoman empire closed off the Silk Road in 1453 CE, Western European countries such as France, Spain, and Great Britain sent explorers all over the world in search of new trade routes and new lands. These explorers paved the way for "Western" culture to spread all throughout the world, from the newly "discovered" Americas to the islands of Oceania. This mass exportation of culture to the rest of the world came to be known as "Westernization."
By the mid-20th century, Western culture had become widespread throughout the world with the help of mass media, such as television, film, radio, and music. The term "Western culture" is used broadly to refer to traditions, social norms, religious beliefs, technologies, and political systems. Because the culture is so widespread today, the term "Western World" has taken on a cultural, economic, and political definition—but those definitions can differ from one another.
In the aftermath of World War II, "Western World" took on a new political definition: It was used to describe countries that had democratic, capitalist governments and were aligned alongside the United States, France, and the United Kingdom. Also referred to as "First World countries" or the "Cold War West," this group of nations stood in contrast to the Second World countries of the U.S.S.R.-led communist Soviet bloc.
One lesser-known modern variation of the Western World is the "Rich West," which is specifically used when discussing and comparing national economies. By this definition, Western World includes European-settled countries with GDPs per capita higher than US$10,000. This threshold excludes many Central and South American countries included in the other definitions but includes several former communist countries that were not part of the Cold War West.
Today, the most widely used definition of the Western World, also known as the "Latin West," is based entirely on culture rather than geography. In this usage, Western World refers to all of the countries of Western Europe, as well as those countries shaped by Western European culture. For example, countries such as the United States and Australia, which were once British colonies and which adopted Western European Christianity (Catholic and Protestant churches), which use the Latin alphabet, and whose populations include many people descended from European colonists.
In practical terms, this means the Western World typically includes most countries of the European Union as well as the U.K., Norway, Iceland, Switzerland, the United States, Canada, Australia, and New Zealand. However, there are also two sub-regions that may or may not be included. First is the Orthodox World, which collects the countries of Eastern Europe, such as Russia, Greece, and Slovakia. Second is Latin America, which includes Mexico, Peru, and the other countries of Central and South America. As mentioned, these groupings may be considered part of the Western World or may be broken out on their own.
Of course, many countries clearly do not belong to the Western World, the Orthodox World, or Latin America. Most social scientists divide these countries into three overlapping regions: the Eastern World, which includes all of Asia and the Middle East; the Arab World, which comprises the Middle East and North Africa; and Africa, which includes the entire continent of Africa and Madagascar.
The most common use of Western countries refers to Western Europe and the nations heavily influenced by its culture. Examples include Australia, North American nations, and South American countries.