In English most 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), and other geographic expressions (the Netherlands). 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.
Article (grammar - Wikipedia, the free encyclopedia)
Other names of countries used with the definite article :
The Gambia, etc.
Omniglot - the blog » Definite countries
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