In English most cities and countries never take the definite article, but there are many that do. It is commonly used with many country names which derive from names of island groups (the Philippines), mountain ranges (the Lebanon), deserts (the Sudan), seas, rivers and geographic regions (the Middle East). Such use is declining, but for some countries it remains common. Since the independence of Ukraine, most style guides have advised dropping the article, in part because the Ukrainian Government was concerned about a similar issue involving prepositions. Another example is Argentina which is now more usual than 'the Argentine' which is old fashioned.
The definite article is always used for countries whose names are descriptions of the form of the state rather than being purely geographical; for example, the United States, the Soviet Union, the Czech Republic.
The U.S. Department of State and CIA World Factbook show the definite article with only two countries: The Bahamas and The Gambia.
Source: Article (grammar) - Wikipedia, the free encyclopedia
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