Here are the basic rules for the use of articles.
Use a/an before a singular countable noun. Note that a singular countable noun requires an article or another determiner before it.
- I saw a tiger behind the bushes. (NOT I saw tiger behind the bushes.)
- She met a stranger on the road. (NOT She met stranger on road.)
- I have always wanted to become an engineer. (NOT I have always wanted to become engineer.)
Plural and uncountable nouns can be used with or without an article or another determiner.
Use a/an when we use a noun for the first time. Use the when the same noun is used for the second time.
- A man was walking down a street with a dog. The dog ran after a cat. (NOT A dog ran after a cat.)
We use a/an when we wish to express surprise, horror, joy, disgust etc.
- What a lovely flower!
- What a silly fellow!
- What a nice guy!
We use the before a singular noun that is used to refer to a class of people, animals or things.
- The red panda is a cute little creature that resembles a teddy bear.
- The yak is found in Nepal and Ladakh.
We use the before an adjective that refers to a special class of people.
- The government should do something for the poor.
- Mother Teresa cared for the old and the infirm.
We use the before certain numbers like first and second.
- I still remember the first time I met you.