used to 表示过去与现在或过去某时与后来的情况有不同，强调“现已无此习惯了”

 would 只表示过去的情况，与现在无关。

 他年轻时总是吸许多烟。（不含有和现在比较，现在他也许还在抽，也许不抽了。）When he was young he would smoke a lot

 他过去住在乡下，现在住在城里。He used to live in the country but now he lives in the city

 以前凯特非常瘦。Kate used to be very thin

 街道拐角处过去有座楼房，现在拆了。（不用 would ）There used to be a building at the street corner but it has been pulled down

 used to 可泛指过去的习惯动作或状态，

 would 表示过去的习惯动作时，往往要带有一个特定的时间状语。

 我们过去常在田野里玩捉迷藏。 We used to play hide - and - seek in the fields

 每当我们在乡下，我们都在田野里玩捉迷藏。Whenever we were in the country we would play hide - and - seek in the fields

dare 可用作情态动词，也可用作行为动词，指勇气和胆量上的可能，可译为“敢”。

dare 作为情态动词时用于疑问句和否定句，一般不用于肯定句中。

 我不敢在黑夜穿过森林。I dare not walk through the forest at night

 你敢在黑夜穿过森林吗？ Dare you walk through the forest at night?

 是的，我敢。 Yes,  I dare

 不，我不敢。 No,  I daren't

 下雨天他不敢开得太快。He dare not drive too fast on the rainy day

 去年他不敢做这事。He dared not do it last year

 dare， 的过去时为 dared

 我真奇怪他怎么竟敢说出这样的话。I wonder how he dare say such things

 我们不知道他是否敢爬那座山。We don't know whether he dare climb the mountain

 如果敌人敢进入村里，我们就和他们战斗到底。If the enemy dare enter the village we'll fight against them to the end

 如果你们敢在考试中作弊，我就惩罚你们。If you dare cheat in your exam I will give you some punishment

 dare 可以作为行为动词，多用于肯定句中，但也可用在疑问句和否定句中

 他敢面对任何危险。He will dare any danger

 他激我跳过小溪。He dared me to jump over the stream

有人敢于承认吗？Did anyone dare to admit it ?

 我再也不敢返回去看一眼了。（否定句中 to 可省略）I have never dared go back to take a look  

   I have never dared to go back to take a look

和其他行为动词一样， dare 在句子中要随着主语的人称和数发生变化。

 他不敢走夜路。（作行为动词）He doesn't dare to walk at night

 他不敢走夜路。（作情态动词）He daren't walk at night

 他敢走夜路吗？（作行为动词）Does he dare to walk at night?

 他敢走夜路吗?（作情态动词）Dare he walk at night?

 十五年前他不敢走夜路。（作行为动词）He didn't dare to walk at night fifteen years ago

 十五年前他不敢走夜路He daren't walk at night fifteen years ago  

  He dared not walk at night fifteen years ago

明天你敢做同样的实验吗？（作行为动词）Will you dare to do the same experiment tomorrow ？

 明天你敢做同样的实验吗？（作情态动词）Dare you do the same experiment tomorrow ？

 英语口语中 dare 的几个常用结构：

 我想 大概 可能 或许I dare say

 我想情况会好转的。I dare say things will improve

  你怎么敢？How dare you？

 你怎么敢问我这样的问题？How dare you ask me such a question？

 我谅你也不敢I dare you

我谅你也不敢告诉你父母！I dare you to tell your parents !

need 和 dare 一样，作为情态动词时，用于否定句和疑问句，一般不用于肯定句中

作为情态动词，它的词形只有 need 一种形式。

 你现在不必还书，如果愿意，你可以下周还。You needn't return the book now,  You can keep it till next week if you like     

 You don't have to return the book now,  You can keep it till next week if you like

needn't = don't have to

 我现在就要交家庭作业吗？Need I hand in my homework now?

 他要下个星期完成这篇文章吗？ Need he finish the article next week?

 是的，他必须完成。 Yes, he must

 不，他不需要。 No, he needn't    

  No, he doesn't have to

need 和 dare 一样，也可以作行为动词，可用于肯定句、否定句和疑问句中。

行为动词 need 有人称和数的变化。

 植物需要水。Plant needs water

 我的衬衫需要一枚钮扣。My shirt needs a button

 我的车该修理了。My car needs repairing

 他已经长大了，我们不必为他担心。He has grown up,  We don't need to worry about him

 你不必为这次野餐买这么多东西。You don't need to buy so many things for the picnic

 干那工作，需要耐心。Patience is needed for that job