the, a, and an

Definite article: the

The is the definite article. It is used before a noun to refer to a specific one. 

Examples:

• Can you please hand me the green towel? (I only want the green towel.)
• I want the cherry pie. (I want a specific pie.)
• She wants the apple. (I want the specific apple you are holding.)
• I like the elephants at the zoo. (I like those elephants at that zoo.)

Indefinite articles: a/an

A and an are indefinite articles. They are used before nouns to refer to something in general. 

A is used before words that start with a consonant. 
An is used before words that start with a vowel.

Examples:

• Can you please hand me a towel? (It doesn't matter which towel.)
• I want a pie. (I don't care what type of pie.)
• She wants an apple. (She doesn't care which apple.)
• I like an elephant at a zoo. (I don't care which zoo. I am not talking about a specific elephant.)

 

So how do you know when to use each one?

1) Use A or An when

• you mention something for the first time.
  
  Examples:
  • I need a volunteer.
  • We have a winner!
  • Do you have an eraser?
     
• you want to say something belongs to a certain group or category.
  
  Examples:
  • That is a horse.
  • Brownie is a dog.
  • That is an electric car.
     
• you want to say that someone belongs to a certain group.
  
  Examples:
  • Stacy is a girl.
  • He is a student at that high school.
  • Mr. Jones is an electrician.
     
• you want to say that something is "that kind of thing."
  
  Examples:
  • It is a pretty flower.
  • The table is a strong table.
  • It was an early morning.
     
• you want to say that someone is "that kind of person."
  
  Examples:
  • He is a smart teacher.
  • She is an attractive woman.
  • You are a special friend.

2) Use the when

• you talk about a specific thing.
  
  Examples:
  • Did you find the keys to my car?
  • I bought the red bicycle at the bicycle store.
  • The sound I heard was loud!
• it is clear which thing you are talking about.
  
  Examples:
  • She brought the cake!
  • I love the rain.
  • It was the dog!
• there is only one such thing.
  
  Examples:
  • The moon is bright tonight.
  • I love to visit the Atlantic ocean.
  • She is the English teacher.

3) Do not use an article when

• you talk about something general.
  
  Examples:
  • Incorrect: The monkeys are the funny animals!
  • Correct: Monkeys are funny animals!
     
  • Incorrect: Learning the English can be difficult.
  • Correct: Learning English can be difficult.
     
  • Incorrect: The dogs are a man's best friend.
  • Correct: Dogs are man's best friend.
     
• you talk about cities, countries, streets, people, etc.
  
  Examples:
  • Incorrect: She moved from the Kansas.
  • Correct: She moved from Kansas.
     
  • Incorrect: I visited the Mrs. Smith.
  • Correct: I visited Mrs. Smith.
     
  • Incorrect: We live on the Main Street.
  • Correct: We live on Main Street.