Teaching articles is hard. Patterns are hard to find. At least one pattern is easy to teach. Why do we say “America” but “the United States”? The rule is:
Use the if the country’s name includes a common noun.
This rule works for almost every country (one important exception is “the Philippines”). Common nouns are nouns that can mean ordinary things beyond the name. In our examples, the common nouns are state and kingdom. We can say “California is a big state” or “The princess lived in a beautiful kingdom.”
Other country names to consider:
|the Central African Republic|
|the Marshall Islands|
|the Republic of Korea (but South Korea)|
|the Russian Federation (but Russia)|
|the Roman Empire (but Rome)|
This rule can also help you avoid offending some people. We sometimes use the without a common noun when describing a geographic or cultural region. For example, the South, the Outback. If you use the with a country whose name does not include a common noun, it sounds like you consider the country to be just a region. For example, the name “Ukraine” is correct (it does not include a common noun). If you say, “the Ukraine,” you imply that an entire nation is simply a geographic area, and Ukrainians may be offended.