① it代替已經(jīng)提到過的特指單數(shù)可數(shù)名詞,兩者為同一物。
As this chair is broken,I must have it repaired. 這張椅子壞了,我得叫人修理一下。
My father bought a pen and gave it to me. 我父親買了一支鋼筆,給我了。
A:Do you need the book?你需要這本書嗎?
B:Yes,I need it. 對,我需要(它)。
② one用以代替已經(jīng)提過的泛指單數(shù)的可數(shù)名詞,但one和已提過的名詞不是同一物。
我的傘丟了,我得買一把。
I have lost my umbrella and I must buy it.
I have lost my umbrella and I must buy one.
I have no dictionary,so I want to buy one. 我沒有詞典,所以想買一本。
A:Do you need a bike?你需要一輛自行車嗎?
B:Yes,I need one. 是的,我需要一輛。
③ 另外,it可以代替不可數(shù)名詞,而one只能代替可數(shù)名詞單數(shù)。
The wine is too strong,so I can't drink it. 這是度數(shù)太高的烈性酒,所以我不能喝。
This wine is milder than that. 這種酒比那種酒要淡。(不可用 than that one)