In English, World is rooted in a compound of the obsolete words were, man, and eld, age; thus, its oldest meaning is "Age of Man." World can refer to the domain of discourse, but it can also mean many other things:
It is sometimes used to refer to the entire Universe. This is less common now that knowledge of space is more commonplace; however, it is still used vaguely in this sense (as in "the whole wide world").
In another religious sense, in Christianitythe world refers to the fallen and corrupt world order of human society outside the community of believers. The world is frequently cited alongside the flesh and the Devil as a source of temptation that Christians should flee.
In knowledge engineering and knowledge level modeling, the term world refers to a consistent state of beliefs. A system's world is the knowledge that system has about its environment.
Second World refers to nations within the Soviet Union's sphere of influence, e.g. Warsaw Pact countries. Besides the Soviet Union proper, most of Eastern Europe was run by satellite governments working closely with Moscow. This term may or may not also refer to Communist countries whose leadership were at odds with Moscow, e.g. China and Yugoslavia.
Third World refers to nations within neither sphere of influence and were often members of the Non-Aligned Movement. After World War II, the First and Second Worlds struggled to expand their respective spheres of influence to the Third World. The militaries and intelligence services of the United States and the Soviet Union worked both secretly and overtly to influence Third World governments, with mixed success.
There were a number of countries which did not fit comfortably into this neat definition of partition, including Switzerland, Sweden, and the Republic of Ireland, which chose to be neutral. Finland was under the Soviet Union's sphere of influence but was not communist and not a member of the Warsaw Pact. Austria was under United States' sphere of influence, but in 1955, when the country again became a fully independent republic, it did so under the condition that it remained neutral. There was also Berlin which remaind under military occupation.
With the 1991collapse of the Soviet Union and the fall of Leninist, Communism, the term Second World largely fell out of use — though Third World remains popular. The remaining Communist countries either became more isolated from the world economy, as in North Korea and Cuba, or began integrating capitalist concepts such as private enterprise into their societies and forging new trading ties with external capitalist economies, as in Vietnam and China.
There is also the less commonly used term Fourth World, often used to refer to nations that lack any national representation at the UN, but that may enjoy representation at UNPO — indigenous peoples living within or across state boundaries.
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