a, an and the: Correct Grammar Usage

     There are three articles in English grammar; the, a and an. Articles are just small words but it could cause big troubles if used incorrectly.
For example, if you asked your brother to close the door of your room but instead of saying “Close the door.” you accidentally said “Close a door.” then you might be surprised if your brother closed the door of his closet. The use of articles determines the quality of a noun if it refers to a specific noun or any noun. Take a look at these examples:

     The pencil was used to write.

     In this sentence, there is only one pencil available for writing and that pencil is designed to be used specifically for that task.

     A pencil was used to write.

     In this sentence, any pencil may be used to write and not a specific pencil.

     “The” is used to express that a noun is used for a specific thing while “a and an” is used to express that any noun of the same kind may be used or applied.

     Think of it as an ant colony. There is only one queen and there are thousands of ants in an ant colony.

     1. I saw the queen ant came out from the hole.

     2. I saw an ant carrying a leaf towards the hole.

Take a look at more examples below:

a and an

     1. A key is used to open locked doors. (Any key could be used to unlock any door.)

     2. A cat ate the bread on the table. (Any cat might have eaten the bread on the table.)

     3. An airplane landed on the runway. (Any airplane landed on the runway.)

The sentences above express indefinite objects and not specific things.

the

     1. The key on the table is used to unlock my room’s door. (A specific key can unlock the door.)

     2. The caged cat escaped and ran. (Only the caged cat escaped and ran.)

     3. The host announced the winner. (Only the host announced the winner.)

     The sentences above express specific and definite things. We cannot use “a and an” with plural nouns. They are always used with singular nouns in a sentence.