Online Learning 
The Use and Non-Use of Articles

Use of the articles
a, an, and the depends on whether the noun following the article possesses these paired qualities: countable vs. non-countable, definite vs. indefinite, first vs. subsequent mention, and general vs. specific. These topics, as well as the meanings associated with the nonuse or omission of articles, are covered in the following sections of this document:
Countable vs. Non-countable
 
A and an are used if the noun can be counted.
      I ran into a post. (How many posts did you run into? Just one. Therefore, use a.)
       I ate a piece of cake.
       I saw an eagle.
 
The is used when the noun cannot be counted.
      I ran into the water. (How many waters did you run into? 
      The question doesn't make any sense because water is non-countable. 
       Therefore, use the.
     
       I ate the rice.
       I saw the milk spill.
 
Indefinite Articles: a and an  
A and an signal that the noun modified is indefinite, referring to any member of a group. These indefinite articles are used with singular nouns when the noun is general; the corresponding indefinite quantity word some is used for plural general nouns. The rule is:
a + a singular noun beginning with a consonant: a boy
      an + a singular noun beginning with a vowel: an elephant
      some + a plural noun: some girls
Note that in English, the indefinite articles are used to indicate membership in a profession, nation, or religion.
      I am a teacher.
      Brian is an Irishman.
      Seiko is a practicing Buddhist.
 
Definite Article: the  
The definite article is used before singular and plural nouns when the noun is particular or specific. The signals that the noun is definite, that it refers to a particular member of a group. Compare the indefinite and definite articles in the following pairs:
A dog (any dog)
The dog (that specific dog)
A book (any book)
The
book (that specific book)
The is used with both singular and plural nouns:
the book, the cat
the books, the cats
The is not used with non-countable nouns referring to something in a general sense:
[no article] Coffee is a popular drink.
[no article] Japanese was his native language.
[no article] Intelligence is difficult to quantify.
The is used with non-countable nouns that are made more specific by a limiting modifying phrase or clause:
The coffee in my cup is too hot to drink.
The Japanese he speaks is often heard in the countryside.
The intelligence of animals is variable but undeniable.
The is also used when a noun refers to something unique:
the White House
the theory of relativity
the 1999 federal budget
Geographical uses of the
Do not use the before:
 names of countries, except the Netherlands and the US (Italy, Mexico, Bolivia)
 names of cities, towns, or states (Seoul, Manitoba, Miami)
 names of streets (Washington Blvd., Main St.)
 names of lakes and bays, except with a group of lakes like the Great Lakes
 names of mountains, except with ranges of mountains like the Andes or the Rockies or unusual names.
 names of continents (Asia, Europe)
 names of islands except with island chains like the Aleutians, the Hebrides, or the Canary Islands (Easter Island, Maui, Key West)
  Do use the before:
        names of rivers, oceans and seas
        points on the globe
        geographical areas
 
deserts, forests, gulfs, and peninsulas
First vs. Subsequent Mention
A or an is used to introduce a noun when it is mentioned for the first time in a piece of writing. The is used afterward each time you mention that same noun.
There is and there are can be used to introduce an indefinite noun at the beginning of a paragraph or essay.
General vs. Specific
A, an, and the can all be used to indicate that a noun refers to the whole class to which individual countable nouns belong. This use of articles is called generic, from the Latin word meaning "class."
A tiger is a dangerous animal. (any individual tiger)
The tiger is a dangerous animal. (all tigers: tiger as a generic category)
The difference between the indefinite a and an and the generic a and an is that the former means any one member of a class while the latter means all of the members of a class.
The omission of articles also expresses a generic (or general) meaning:
no article with a plural noun: Tigers are dangerous animals. (all tigers)
no article with a non-countable noun: Anger is a destructive emotion. (any kind of anger)
 Omission of Articles
While some nouns combine with one article or the other based on whether they are countable or non-countable, others simply never take either article. Some common types of nouns that don't take an article are:
Names of languages and nationalities
          Chinese
          English
          Spanish
Russian
Names of sports
          volleyball
          hockey
baseball
Names of academic subjects
         mathematics
         biology
         history
         computer science