a和an用法順口溜：不定冠詞a和an,單數可數名詞前;輔音若在詞首發,詞前只把a來加;元音若在詞首放,詞前an詞不敢忘;不定冠詞相當one,但不強調數觀念;不定冠詞很關鍵,四個所指記心間.(每指、泛指、類指和某指)。
擴展資料。
不定冠詞a/an的用法：
不定冠詞有兩個，a 和 an。a用在輔音開頭的'單詞前面;an用於以元音開頭的單詞前。如：a book,an apple。具體用法如下：
1)表示「一個」、「某一個」、「 每一」、「再一，又一」、或「同一，相同」等。
eg：
rome is not built in a day
a mr.smith is waiting for you at the school gate
he usually works eight hours a day
you can try it a second time if you fail
they are of an age./ birds of a feather flocks together
2)泛指某一類人或物，意為「任何一個，任一」
eg:
a square has four sides
3)當物質名詞具體化表示「一(類、陣、份)」等;抽象名詞具體化為「……的人或者事」時。
eg:
green tea is a wonderful tea
we don』t have much rain here,but last night we had a heavy rain
reading is a pleasure for me
the meeting is a great success
4)表示季節、月份、日期、三餐的名詞，或表示世上獨一無二的物體名詞前有形容詞修飾時：
eg:
we have a every cold winter last year
this happened on a rain sunday towards the end of may
we hope we can see a full moon tonight
5)源於動詞的名詞與take/have 連用時：
take a look;take a walk;have a break;have a visit to…。
擴展資料。
不定冠詞a/an的用法：
不定冠詞有兩個，a 和 an。a用在輔音開頭的'單詞前面;an用於以元音開頭的單詞前。如：a book,an apple。具體用法如下：
1)表示「一個」、「某一個」、「 每一」、「再一，又一」、或「同一，相同」等。
eg：
rome is not built in a day
a mr.smith is waiting for you at the school gate
he usually works eight hours a day
you can try it a second time if you fail
they are of an age./ birds of a feather flocks together
2)泛指某一類人或物，意為「任何一個，任一」
eg:
a square has four sides
3)當物質名詞具體化表示「一(類、陣、份)」等;抽象名詞具體化為「……的人或者事」時。
eg:
green tea is a wonderful tea
we don』t have much rain here,but last night we had a heavy rain
reading is a pleasure for me
the meeting is a great success
4)表示季節、月份、日期、三餐的名詞，或表示世上獨一無二的物體名詞前有形容詞修飾時：
eg:
we have a every cold winter last year
this happened on a rain sunday towards the end of may
we hope we can see a full moon tonight
5)源於動詞的名詞與take/have 連用時：
take a look;take a walk;have a break;have a visit to…。