Using indefinite articles: a or an
Use a or an when introducing a singular noun for the first time.
This is a book.
This is a computer.
Use an for singular nouns that begin with a vowel (a, e, i, o, or u) or a vowel sound.
This is an orange.
This is an umbrella.
I will be finished in an hour.
In that last sentence, the noun begins with an h, but because the h is silent, the beginning sound you hear is the o.
You should also use a or an when talking about your job or any other group of which you are a member.
I'm an English instructor.
Sandy is a sales associate.
I'm a Christian.
If the noun is preceded by an adjective that begins with a vowel sound, you should use an.
Mike is an honest man.
Sharon is wearing an orange blouse.
Use an when saying acronyms or initials that begin with a vowel sound.
He used to be an IBM employee.
An EEOC member will come to our meeting today.
Use a if the noun starts with a vowel that makes a consonant sound.
Pierre wants to be a United States citizen.
Jonathan is fighting for a uniform that is easy to clean.
In these examples, the u in united and uniform sounds like a y (/yo͞oˈ nīdəd/, / ˈyo͞onə fôrm/) so we used a instead of an.
We never use an indefinite article before an uncountable noun.
x I'd like to order a rice with my meal.
x Can I get a water?
Using the definite article: the
Use the when talking about a specific singular noun or something (or someone) already known.
The book is on the table next to the receptionist.
The computer is on my desk.
Use the when talking about uncountable nouns.
This house has been closed up for a long time so the air is stale.
The sand on this beach is pink!
Use the for specific plural nouns.
The oranges are on the counter in the kitchen.
The umbrellas are in the accessory department.
Using the zero article: Ø
Do not use an article (Ø) when talking about people or things in general.
Ø Libraries are filled with Ø books.
Ø Computers are easy to use.
Do not use an article (Ø) when talking about proper nouns.
Ø Sony is a popular brand.
Ø I’m going to visit Ø Bill Gates at Ø Microsoft next year.
Do not use an article (Ø) with the following:
Names of languages and nationalities: Chinese, English, Spanish, Russian (unless you are referring to the population of the nation. For example, "The Japanese are known for their politeness.")
Names of sports: (Ø) volleyball, (Ø) hockey, (Ø) baseball, etc.
I love to play (Ø) football.
(Ø)Volleyball is my favorite sport.
Names of academic subjects: math, science, social studies, etc.
I'm not good in (Ø) math.
We're having a quiz in (Ø) science today.
Using articles with geography
There are some specific rules regarding using articles when talking about geography.
Use the before the following:
names of rivers, oceans and seas (the Nile, the Pacific)
points on the globe (the Equator, the North Pole)
geographical areas (the Middle East, the West)
deserts, forests, gulfs, and peninsulas (the Sahara, the Persian Gulf, the Black Forest, the Iberian Peninsula)
Do not use the before the following:
names of countries (except with some countries such as the Bahamas, the United States, the Maldives, the United Kingdom and a few others.)
names of cities, towns, or states
names of streets
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 such as the Matterhorn)
names of continents
names of islands (except with an island chain, such as the Aleutians, the Hebrides, or the Canary Islands, or if the name of the island follows, as in The Island of Vancouver or The Isle of Wight)