1.不定冠詞a (an)與數(shù)詞one 同源,是"一個"的意思.a用于輔音音素前,一般讀作[e],而an則用于元音音素前,一般讀做[en].
1) 表示"一個",意為one；指某人或某物,意為a certain.
A Mr.Ling is waiting for you.
2) 代表一類人或物.
A knife is a tool for cutting with.
Mr.Smith is an engineer.
3) 詞組或成語.
a little / a few / a lot / a type of / a pile / a great many / many a / as a rule / in a hurry / in a minute / in a word / in a short while / after a while / have a cold / have a try / keep an eye on / all of a sudden
2.定冠詞the與指示代詞this,that同源,有"那（這）個"的意思,但較弱,可以和一個名詞連用,來表示某個或某些特定的人或東西.
1）特指雙方都明白的人或物：
Take the medicine.把藥吃了.
2）上文提到過的人或事：
He bought a house.I've been to the house.
他買了幢房子.我去過那幢房子.
3）指世上獨一物二的事物：
the sun,the sky,the moon,the earth
4）單數(shù)名詞連用表示一類事物,如：the dollar 美元;
the fox 狐貍；或與形容詞或分詞連用,表示一類人：the rich 富人; the living 生者.
5）用在序數(shù)詞和形容詞最高級,及形容詞only,very,same等前面：
Where do you live?I live on the second floor.你住在哪?我住在二層.
That's the very thing I've been looking for.那正是我要找的東西.
6）與復數(shù)名詞連用,指整個群體：
They are the teachers of this school.指全體教師)
They are teachers of this school.(指部分教師)
7）表示所有,相當于物主代詞,用在表示身體部位的名詞前：
She caught me by the arm..她抓住了我的手臂.
8）用在某些由普通名詞構(gòu)成的國家名稱、機關(guān)團體、階級、等專有名詞前：
the People's Republic of China 中華人民共和國
the United States 美國
9）用在表示樂器的名詞之前：She plays the piano.她會彈鋼琴.
10) 用在姓氏的復數(shù)名詞之前,表示一家人：
the Greens 格林一家人 (或格林夫婦)
11) 用在慣用語中：
in the day,in the morning (afternoon,evening),the day after tomorrow
the day before yesterday,the next morning,
in the sky (water,field,country)
in the dark,in the rain,in the distance,
in the middle (of),in the end,
on the whole,by the way,go to the theatre