The term Western world, the West or the Occident (Latin: occidens -sunset, -west, as distinct from the Orient) can have multiple meanings dependent on its context (e.g., the time period, or the regional social situation). Accordingly, the basic definition of what constitutes “the West” varies, expanding and contracting over time, in relation to various historical circumstances. Historically, the West originated in the northern and eastern Mediterranean with ancient Greece and ancient Rome. Over time, their associated empires grew first to the east and south conquering many older civilizations, and later to the north and west to include Central and Western Europe. Between the fall of the Western Roman Empire and the Renaissance, the West experienced a period of relative decline, known as the Middle ages, which included the Dark ages and the Crusades. The knowledge of the ancient Western world was preserved and survived during this period due to the concurrent ascendency of the Islamic Golden Age to the east and south.

Since the Renaissance, the West evolved beyond the influence of the ancient Greeks and Romans due to the growth of Western European empires, and particularly the globe-spanning British Empire of the eighteenth and nineteenth centuries. Since the Age of discovery and Columbus, the notion of the West expanded to include the Americas, though much of the Americas have considerable pre-Western cultural influence. Australia, New Zealand, and South Africa are considered part of Western culture due to their former status as colonies of Western nations. In addition, Israel and Lebanon may be considered part of the West due to their geographic location and late European colonial origins in the early twentieth century. Generally speaking, the current consensus would locate the West, at the very least, in the cultures and peoples of Europe, North America, Australia, and New Zealand.

In a linguistic context, the languages of most nations of the West are members of the Indo-European language family. It should be noted, however, that the Indo-European languages are not exclusively, or even mainly Western; Persian, Pashto, Urdu and Sanskrit are Indo-European languages as well. There are several linguistic exceptions within the West, including Semitic languages, predominantly Arabic and Hebrew, which are members of the Afro-Asiatic language family, as well as Basque, whose linguistic family is completely unknown.

In a religious context, some would define the Abrahamic religions of Judaism, Christianity and Islam as 'Western'. This context would include some Islamic nations, which are not generally considered to be part of the West in a political or cultural sense, but which are also included in the linguistic sense, noted above.

In the current political or economic context the term the "West" often includes developed nations in the East, such as Japan, Taiwan and South Korea. However, these nations have different and distinctive cultures, religions (although Christianity is a major religion in South Korea), languages, customs, and worldviews that are products of their own indigenous development, rather than solely Western influences. Japan, in particular, is a founding member of the G8, a member of the OECD, an industrialized democracy, with a high standard of living, high level of human development and a major economic power. All of these are generally accepted political or economic characteristics of Western nations.

There is debate among some as to whether Eastern Europe is in a category of its own. Culturally Eastern Europe, although having mainly eastern orthodox and Islamic influences, is usually more or less accepted into the 'West', mainly because of its geographic location in what is mostly Europe (and cultural ties). It, however, does not fill the traditional economic and living standard criteria which one associates with "The West". Broek and Webb, A Geography of Mankind (2nd ed., 1973) at 199, 201; cf., Arnold Toynbee, Change and Habit (Oxford Univ., 1966).