About artical we study article is a kind of adjective which is always used with and gives some information about a noun. There are only two articles a and the, but they are used very often and are important for using English
The word a (which becomes an when the next word begins with a vowel - a, e, i, o, u) is called the indefinite article because the noun it goes with is indefinite or general. The meaning of the article a is similar to the number one, but one is stronger and gives more emphasis. I have a book or I have one book, but the second sentence emphasizes that I do not have two or three or some otbooks 
