Articless

The Articles

The three articles — a, an, the — are a kind of adjective. The is called the definite article because it usually precedes a specific or previously mentioned noun; a and an are called indefinite articles because they are used to refer to something in a less specific manner (an unspecified count noun). These words are also listed among the noun markers or determiners because they are almost invariably followed by a noun (or something else acting as a noun).

CAUTION! Even after you learn all the principles behind the use of these articles, you will find an abundance of situations where choosing the correct article or choosing whether to use one or not will prove chancy. Icy highways are dangerous. The icy highways are dangerous. And both are correct.

When to use A, An or The?
Definite Article - "The" is a definite article, which means that it is used to specify something specific. It refers to a noun the is either understood (by the reader or listener) or has been previously referred to by the writer or speaker.

Indefinite Articles - "A" and "An" are indefinite articles. The difference between "A" and "An". "An":is used is it comes after a word that starts with a vowel.

"A" and "an" are used the same way grammatically. They are used before a singular noun, or before the adjective the represents the noun. They can't be used with plural nouns or uncountable nouns.

Examples

A/An	There is a dog outside the building.	We don't know which dog the writer/speaker is referring to.
The	The black dog is outside the building.	It is understood to which dog the writer/speaker is referring to
A/An	Do you know where there is a post office?	The writer/speaker is not referring to a specific post office
The	I am going to the post office.	It is understood to which post office the speaker/writer is referring to.

The is used with specific nouns. The is required when the noun it refers to represents something that is one of a kind:

The moon circles the earth.

The is required when the noun it refers to represents something in the abstract:

The United States has encouraged the use of the private automobile as opposed to the use of public transit.

The is required when the noun it refers to represents something named earlier in the text. (See below..)

We use a before singular count-nouns that begin with consonants (a cow, a barn, a sheep); we use an before singular count-nouns that begin with vowels or vowel-like sounds (an apple, an urban blight, an open door). Words that begin with an h sound often require an a (as in a horse, a history book, a hotel), but if an h-word begins with an actual vowel sound, use an an (as in an hour, an honor). We would say a useful device and a union matter because the u of those words actually sounds like yoo (as opposed, say, to the u of an ugly incident). The same is true of a European and a Euro (because of that consonantal "Yoo" sound). We would say a once-in-a-lifetime experience or a one-time hero because the words once and one begin with a w sound (as if they were spelled wuntz and won). Merriam-Webster's Dictionary says that we can use an before an h- word that begins with an unstressed syllable. Thus, we might say an hisTORical moment, but we would say a HIStory book. Many writers would call that an affectation and prefer that we say a historical, but apparently, this choice is a matter of personal taste.

For help on using articles with abbreviations and acronyms (a or an FBI agent?), see the section on  
If you would like help with the distinction between count and non-count nouns, please refer to Count and Non-Count Nouns.Abbreviations.
First and subsequent reference: When we first refer to something in written text, we often use an indefinite article to modify it.

A newspaper has an obligation to seek out and tell the truth.

In a subsequent reference to this newspaper, however, we will use the definite article:

There are situations, however, when the newspaper must determine whether the public's safety is jeopardized by knowing the truth.

Another example:
    "I'd like a glass of orange juice, please," John said.
    "I put the glass of juice on the counter already," Sheila replied.

Exception:
When a modifier appears between the article and the noun, the subsequent article will continue to be indefinite:
    "I'd like a big glass of orange juice, please," John said.
    "I put a big glass of juice on the counter already," Sheila replied.

Generic reference: We can refer to something in a generic way by using any of the three articles. We can do the same thing by omitting the article altogether.

• A beagle makes a great hunting dog and family companion.
• An airedale is sometimes a rather skittish animal.
• The golden retriever is a marvelous pet for children.
• Irish setters are not the highly intelligent animals they used to be.

The difference between the generic indefinite pronoun and the normal indefinite pronoun is that the latter refers to any of that class ("I want to buy a beagle, and any old beagle will do.") whereas the former (see beagle sentence) refers to all members of that class.

Proper nouns: We use the definite article with certain kinds of proper nouns:

• Geographical places: the Sound, the Sea of Japan, the Mississippi, the West, the Smokies, the Sahara (but often not when the main part of the proper noun seems to be modified by an earlier attributive noun or adjective: We went swimming at the Ocean Park)
• Pluralized names (geographic, family, teams): the Netherlands, the Bahamas, the Hamptons, the Johnsons, the New England Patriots
• Public institutions/facilities/groups: the Wadsworth Atheneum, the Sheraton, the House, the Presbyterian Church
• Newspapers: the Hartford Courant, the Times
• Nouns followed by a prepositional phrase beginning with "of": the leader of the gang, the president of our club

Abstract nouns: Abstract nouns—the names of things that are not tangible—are sometimes used with articles, sometimes not:

• The storm upset my peace of mind. He was missing just one thing: peace of mind.
• Injustice was widespread within the judicial system itself. He implored the judge to correct the injustice.
• Her body was racked with grief. It was a grief he had never felt before.

Zero articles: Several kinds of nouns never use articles. We do not use articles with the names of languages ("He was learning Chinese." [But when the word Chinese refers to the people, the definite article might come into play: "The Chinese are hoping to get the next Olympics."]), the names of sports ("She plays badminton and basketball."), and academic subjects ("She's taking economics and math. Her major is Religious Studies.")
When they are generic, non-count nouns and sometimes plural count-nouns are used without articles. "We like wine with our dinner. We adore Baroque music. We use roses for many purposes." But if an "of phrase" comes after the noun, we use an article: "We adore the music of the Baroque." Also, when a generic noun is used without an article and then referred to in a subsequent reference, it will have become specific and will require a definite article: "The Data Center installed computers in the Learning Center this summer. The computers, unfortunately, don't work."

Common count nouns are used without articles in certain special situations:

idiomatic expressions using be and go	We'll go by train. (as opposed to "We'll take the train.) He must be in school.
with seasons	In spring, we like to clean the house.
with institutions	He's in church/college/jail/class.
with meals	Breakfast was delicious. He's preparing dinner by himself.
with diseases	He's dying of pneumonia. Appendicitis nearly killed him. She has cancer (You will sometimes hear "the measles," "the mumps," but these, too, can go without articles.)
with time of day	We traveled mostly by night. We'll be there around midnight.