Article usage depends on whether a noun is one of the following:

  1. singular or plural
  2. indefinite or definite
  3. countable or uncountable
     

A.  The indefinite articles a and an are used with indefinite nouns.  An indefinite noun refers to a thing that is not specifically identified.  An indefinite noun is unknown either to you, the reader, or to the writer of the text.  A and an mean one.  Use a/an only with singular countable nouns. Never use a/an with plural nouns. Never use a/an with uncountable nouns.
 

Singular countable nouns:

Nouns that represent a whole class or type of things:

  • The chill of an ice storm can be felt inside as well as outside.
  • An ophthalmologist is a doctor who specializes in the structure and diseases of the eye.
     

A or An? Use a before a consonant sound. Use an before a vowel sound:

a hurricane an American an oil derrick
a wild animal an invention an uprising
a year ago an economics professor an unusual request



Some words are spelled with a vowel but are pronounced with a consonant sound:

a European a university a useful example
a eulogy a uniform a utility vehicle



B.  The definite article, the, is used with definite nouns. A definite noun refers to a thing that is known to you, the reader. A definite noun can be made known by being mentioned in the sentence.  A definite noun is specific rather than general. Use the with a singular and plural countable nouns and with uncountable nouns:
 

Singular countable nouns:

  • The gearbox of a gasoline engine lies between the clutch and the differential.
     

Plural countable nouns:

  • The crankshaft always turns faster than the wheels.
     

Uncountable Nouns:

  • The police discovered the information about the suspect on Facebook.

  • Good teachers care about the progress of their students.
     

Use the with other nouns and structure

Specific species of animals and plants:

  • The humpback whale migrates between its summer feeding ground in Alaska and its winter breeding and calving ground in California, Mexico.

  • The dogwood is the provincial flower of British Columbia.
     

Inventions, instruments, models, and types of buildings:

  • The elevated floors of the AQ contain academic departments, offices and classrooms.

  • The World Wide Web was invented by Tim Berners-Lee in Switzerland in 1989.

  • The trombone is a musical instrument in the brass family.
     

Superlatives and one of:

  • The oldest playable musical instrument is a 9,000 year old flute discovered in China.

  • SFU is one of Canada’s best comprehensive universities.
     

The only one of something:

  • The Sun is by far the largest object in the solar system.
     

Body parts:

  • Pneumonia is an inflammatory illness of the lungs.

  • The human brain contains 10 billion neurons, mostly in the outer layer of the brain cortex.
     

Names of large bodies of water, regions, groups of mountains, islands, and lakes:

the Pacific Ocean the Panama Canal the Ural Mountains the Fraser River
the West the Pacific Rim the Great Lakes the Caribbean



C.    No article is used with some nouns:
 

Plural countable nouns that are indefinite:

  • Stanley Park is an urban park containing many beaches, trees, and trails.
     

Generalizations about uncountable nouns:

  • Land, labor, and capital are essential for the production of goods.

  • Human Kinetics is the study of the human body and its relationship to exercise, sport, and health.
     

Gerund (verb + ing):

Gerunds are usually uncountable and indefinite, as in:

  • Myanmar ruby mining is done by a mixture of all tribes and ethnic groups of Myanmar.
     

Exception: A gerund + of structure is made specific and therefore takes the definite article the:

  • The mining of rubies is Myanmar's third largest export, netting close to US $300 million