Electric Transportation

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. It is possible to say I have a book or I have one book, but the second sentence emphasizes that I do not have two or three or some other number of books.