成人英語三級考試詞彙與語法
1、can
1)表能力時意味着憑體力或腦力或技術等可以無甚阻力地去做某事。
I can climb this pole. 我能爬這根杆子。
He is only four, but he can read. 他只有4歲，但已認得字了。
2)表示推測語氣的用法時，can只能用於疑問句和否定句，用於否定句的時候必須要有充分的理由説明。如：
Can he be at home? No, he can't be at home, because I met him in the street just 5 minutes ago.
他可能在家嗎?不，他不可能在家，因為我5分鐘之前才在街上遇到他。
2、may (might)
1)表示請求、可以、允許。
You may drive the tractor. 你可以開那台拖拉機。
2)表建議(可和as well 連用)
You may (might) as well stay where you are.
你還是原地待着好。(may as well 有“還是……的.好”的含義)
3)表可能(事實上)。可以指過去時間，也可以指現在時間，但語氣更加不肯定，只能用於肯定句和否定句。
He may be at home. 他可能在家。
She may not know about it. 她可能不知道這件事。
He was afraid they might not agree with him. 他擔心他們可能不同意他的意見。
They might be having a meeting, but I'm not sure. 他們有可能在開會，不過我不肯定。
3、must
1)表示必須、必要
We must do everything step by step. 我們必須按部就班地做一切事情。
2)must 的否定式有兩個：當回答由must引起的問題時，否定答覆要用needn't或don't have to表示“不必”、“無須”、“用不着”
3)表示推測語氣的用法，意為“準是、一定”等，只用於肯定句，並且要有充足的理由説明。
He must have passed the exam, because he looked so happy.
他一定通過考試了，因為他看起來如此的開心。
4. have to
have to的含義與must是很接近的，只是have to 比較強調客觀需要，must着重説明主觀看法。
I must clean the room.(主觀想法)I have to clean the room.(客觀需要)
另外，have to 能用於更多時態：
We had to be there at ten. 我們得在十點鐘到那裏。
We will have to reconsider the whole thing. 這一切我們將不得不重新加以考慮。
have to 的否定式：don't have to do 表示“不必做……”之意。
5、would
1)表意願。
They would not let him in because he was poorly dressed. 他們不讓他進去因為他衣着破舊。
I said I would do anything for you. 我説過我願意為你做任何事。
2)表過去反覆發生的動作或過去的一種傾向。
Every time she was in trouble, she would go to him for help.
她每遇到麻煩都會向她求助。他告訴我盒子打不開了。
6、ought to
表義務，意為“應該”(因責任、義務等該做)，口氣比should稍重。
You are his father. You ought to take care of him. 你是他父親，應當管他。
You oughtn't to smoke so much. 你不應該抽這麼多煙。
7、used to
表示過去的習慣動作或狀態，現在不復發生或存在。疑問式和否定式有兩種。
He used to live in the countryside, but now he lives in the city.他過去住在鄉下，現在住在城裏。
There used to be a building at the street corner, but it has been pulled down.
街道拐角處過去有座樓房，現在拆了。
I usedn't (didn't use) to smoke. 我過去不抽煙。
Used you (Did you use) to go to school on foot? 你過去常步行去學校嗎?
