Unfortunately, the last Final Test for advanced students, which took place at the beginning of January 2009, confirmed it again and again. Even very good students made mistakes when concerning articles.
English has just two types of articles: definite (the) and indefinite (a, an). In spite of this learning articles is a hard nut to crack for ESL (English as 2nd Language) students. Nevertheless, it is not difficult to understand their usage and articles can be learnt with practice. Only it is necessary to sense the existence of articles in English. English has articles and their role is very important.
Linguists believe that the common ancestor of the Indo-European languages did not have articles. Most of the languages in this family do not have articles just now; there is no article in some modern Indo-European languages, especially in Slavic languages – Russian, Slovak and Czech etc. (the only Slavic languages that have articles are Bulgarian and Macedonian), in the Baltic languages – Latvian, Lithuanian and Latgalian. So mistakes with the use of the and other determiners are common for people learning English as ESL and whose native language does not involve articles. In the etymologies of many other languages, the definite article arose by a demonstrative pronoun or adjectives. In English the and that originated as a result of common developments from the same Old English system, which had definite articles for formerly existed genders.
Old English (also called Anglo-Saxon sometimes) is an early form of the English language that was spoken and written in parts of what are now England and south-eastern Scotland between the mid-5th century and the mid-12th century. In Middle English these had all merged into þe, and later into the word the, i.e. the definite article in Modern English.
It depends mainly on whether you are referring to any member of a group, or to a specific member of a group:
The English indefinite article reflects its roots in the number word one. Therefore it can only be used with singular countable nouns. A (an) signals that the noun refers to any member of a group as follows (the examples are taken from the Purdue University Online Writing Lab):
If the noun is preceded by adjectives, the choice between a and an depends on the initial sound of the adjective that immediately follows the article:
Moreover, in English, the indefinite article is used to indicate membership in a profession, nation, or religion.
* I am a teacher.* Brian is an Irishman.* Seiko is a practicing Buddhist.
The only definite article in English the is also the most frequently used word in the English language.
The is used with singular and plural, countable and uncountable nouns when both the speaker and listener know the thing or idea already. The indicates that the noun is definite, that it refers to a particular member of a group (see details on Purdue University Online Writing Lab). The is also used when a noun refers to something unique:
* the White House* the theory of relativity* the federal budget
Further, use of a, an, and the depending on whether the noun following the article holds one of these paired qualities:
A tiger is a dangerous animal. (any individual tiger)
The tiger is a dangerous animal. (all tigers: tiger as a generic category).
Reduction and omission
In news headlines and informal writing, such as notes or diaries, the articles and some other particles are often omitted, for example, “Must pick up prescription at pharmacy today.“
In English as a rule most cities and countries never take the definite article. Nevertheless, in general it is 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).
The definite article is always used before compound names of the country, e.g. the United States, the Soviet Union, the Czech Republic.
Find very good and cogent review of English articles use in “A, An, The” definite and indefinite articles in English – Beginning Guide … .