Why 'The' is used? [duplicate]

Possible Duplicate:
Using the definite article before a country/state name

Why do we write:

The UCI Road World Championships 2012 (when the year is mentioned)

The Republic of India (when there is only one nation) but NOT The India?

The Monaco Grand Prix (only one place which holds GP with that name)

Lake Baikal in South of the Russia (why not Lake Baikal in the Russia?)

I know the answer: The grammar usage is Definite Article but I'm looking for a clear explanation to this question.

Solution 1:

The article the is usually used when the reference includes a word that can be a common noun and not just a proper noun, or when the proper element is an adjective.

Using the article

the United States
the British Commonwealth
the Time-Warner Building
the Republic of India
the Malay Peninsula

Not using the article

America
England
Time-Warner
India
Malaysia

This is far from universal, since you could say

Time-Warner Corporation
the Time-Warner Corporation

Occasionally phrases using identical words either use or omit the article depending on the word order

the State of New York
New York State

In this case, when the first word is a common noun, the article is used, when a proper noun (or part of a proper noun) the article is omitted.

Lakes seem to be an exception. In US we say

Lake Superior
Lake Louise

However, we tend to say

the Mississippi River
the River Jordan
the Jordan River
the Atlantic Ocean