The Use of A, An and The

A, an and The mostly called as article. Now we will share the use of a, an and the in English.
1. A
is used to mention thing in singular. Mostly it is used when thing starts with consonant letter; however, sometimes it is used when the pronunciation of thing is consonant sound.
Example:
a. This is a book (consonant letter)
b. He studies in a university (consonant sound) uni= yuni
c. Spain is a Europe country (consonant sound) Europe = Yoo-rop

2. An
is used to mention thing in singular when it begins with vowel letter or vowel sound 
Example:
a. This is an apple (vowel letter)
b. Andi is studying for an hour (vowal sound) hour = auer

3. The
is used to mention thing in singular or plural but specific or particular one. Easily, it can be said that we use the when the speaker and listener know about the thing.
Example :
Made: where is my book?
Wayan:I am sorry, I am reading the book
means that Made's book is the same book that Wayan read.

Komang: I kiss the girl yesterday
Ketut: How Lucky your are to kiss her!
means that komang and ketut mention the same girl or komang and ketut know whom girl kissed by Komang

last one
She cleaned the table ( she clean the table which known by the listener)
She cleaned a table ( table can be every table not specific one)