Reason: After A or an, see if the first phonetic symbol of the following word is consonant or vowel. The useful phonetic symbol is [`ju:sful], so it is followed by a.
A is used before the words at the beginning of consonant pronunciation, not before consonant letters, such as a book and a desk; An is used before the word that starts with the vowel sound, not before the vowel letter, such as: an apple, an hour.
Although some words begin with consonants, their pronunciation begins with vowels. These words can be combined into one sentence: an honest man accepted a glorious task an hour ago.
First, it is useful
English [? Ju:sfl] Beauty [? jusf？ l】？
Useful, beneficial, and helpful; satisfactory
Second, books.
English [b]? K] beauty [b? k]？
Noun (short for noun)
Books; Volume; Textbooks; account book
That is a useful book for people who think about literary life. ?
It is a useful book for people who want to engage in literary life.
Where can I buy such a useful book? & I have two such books. I can give you one. ?
Where can I buy such a useful book? I have two. I can give you one.
Extended data
Special usage of a and an:
1. Although the first letter of some words begins with a vowel, when their pronunciation begins with a consonant phoneme, the article in front of them can't use an like the word that begins with a vowel, but should use the article A. ..
Although the word "useful" begins with the vowel letter U, its pronunciation is based on the consonant factor [? jusf？ L], so it can't be preceded by the article an, but the article a.
Although the first letter of some words begins with a consonant, when its pronunciation begins with a vowel phoneme, the article before it should be an instead of a. ..
Although the word "hour" begins with the consonant letter H, its pronunciation is vowel phoneme [a? R], so he can't use the article a in front of him, he should use the article an.