1．persuade vt. 说服；劝服，使某人相信（advise…successfully）
主要用法：
persuade sb. of sth. 使某人相信某事（make sb. believe in sth.）相当于persuade sb. that….
persuade sb. to sth. 劝服某人接受某事
例如：
He persuaded me not to drop the experiment.
他劝得我打消了中断试验的想法。
（相当于：He persuaded me out of the idea of dropping the experiment.）
The salesman persuaded us to buy his product.
这推销员说服我们买下了他的产品。
（相当于：The salesman persuaded us into buying his product.）
How can I persuade you of my sincerity?
我如何使你相信我的诚意？
(相当于：How can I persuade you that I am sincere?)
2．discourage vt. 使泄气；使失去信心（make…lose heart）
discouragement n.
主要用法：
sb. / sth. discourage sb.某人/某事使某人泄气（sb. be discouraged by sb./ sth.）
sb. / sth. be discouraging 令人泄气的人或物
sb. be discouraged 感到泄气的人或物
discourage sb. from doing sth. 阻止某人去做某事
discourage doing sth. 阻止做某事
反义词：encourage v. encouragement n.
例如：
This new is discouraging. 这则消息令人失望。
This boy is discouraging. 这男孩令人失望。
This news discouraged me. 这消息令我失望。
We were discouraged by the news. 听到这消息后我们都泄气了。
Mother discouraged me from joining the army. 妈妈阻止我参军。
We discourage smoking in this school. 我们不允许在学校抽烟。
3．via prep. 凭借；通过（某种手段或某人）；经过；经由
主要用法：
（1）途经（某地）（travelling a place on the way）
We went to Shanghai via Hefei and Nanchang.
我们经由合肥和南昌去上海。
（2）通过（……方式/方法）（by means of; using…）
I can read this English novel via the Chinese translation.
我们借助于中文译本读这本英文小说。
（3）借助于（with the help of…）
I sent a letter to Mary via her sister.
我通过玛丽的妹妹带封信给玛丽。
4．suffer from 经受（长期不愉快的事，如疾病等）
主要用法：suffer from 遭遇到损失或患上某种疾病、灾难等
cf. suffer：也可指遭受到损失、不幸等。
注意：如指疾病或主观方面所造成的损失，多用suffer from.
如指客观则可用suffer或suffer from
例如：
She suffers from headaches.
她常头疼。（suffer from＋疾病）
China suffered from a serious flood in 1998
1998年中国遭遇了一场特大洪灾。
Perhaps you suffered from overwork.
或许你是工作过度了。（suffer from＋主观原因）
He is suffering (from) cold and hunger.
他在挨饿，受冻。[ suffer (from) ＋客观]
His work suffered from all his social activities.
他所有的社交活动对他的工作有极大的影响。（suffer from＋主观）
She suffered (from) the loss in the accident.
在这次事故中，她蒙受损失。[suffer (from) ＋客观]
5．lack n. & v. 缺乏，没有；缺少的东西
主要用法：
（1）作动词
（2）作名词，相当于absence，常用于搭配：
because of/ for/through/by/from (a /the) lack of 由于缺乏……
We lack food. 我们缺少食物。（相当于：We are lacking in food.）
The plants died through / for/by/from/because of lack of water.
植物因缺水死亡了。
6．witness vt. 目睹；目击：为……作证
n. 证据；目击者
主要用法：
（1）可指地点或时间见证了某一事件的发生，主语为时间或地点。
The year 1997 witnessed Hong Kong’s coming back to China.
香港在1997年回归到祖国。
Los Angeles witnessed the Olympic Games in 1984.
1984年奥运会在洛杉机举行。
（2）可指某人亲眼目睹某事（的发生过程），可用sb. witness sth.
He witnessed the battle.
他亲眼目睹了那场战斗。
（3）可指“表明，表示，说明”，可用sth. witness sth.
His flushed face witnessed the great excitement he felt.
他通红的脸表明他很激动。
（4）可指“作证说，证明”。
None could witness that he was present.
没有人能证明他在场。
（5）可用作名词，指“证据，证明”。
History is the most telling witness.
历史是最好的见证。
These facts are a witness to his ignorance.
这些事实证明了他的无知。
主句中的should只用于I、we, 但在美国英语中，should常被would 代替；从句中的should可用于各种人称。
1．表示与现在事实相反的假设和结果。
If I were you, I should (would, could, might) tell him the truth.
如果我是你，我就会（可能）对他说实话。
If he had time, he would (could, might) go with you.
如果他有时间，他就会（可能）和你去。
If my brother were here, everything would be all right.
要是我哥哥在这儿，一切都没问题了。
2．表示与过去事实相反的假设和结果。
If you had taken my advice, you wouldn’t (couldn’t) have failed in the exam.
如果你按照我的建议去做，你不会（不可能）考试不及格。
If I had had the money last week, I should (would, could, might) have bought a car.
如果我上星期有了这笔钱，我就会（可能）买一辆车。
She would (could, might) have telephoned you immediately, if she had won the game.
如果她比赛赢了，她就会（可能）给你打电话。
If you had come a few minutes earlier, you would (could, might) have met the famous singer.
如果你早来几分钟的话，你就会（可能会）见到那个著名的歌唱家。
3．表示与将来事实可能相反的假设和结果。
If it were Sunday tomorrow, I should( would, could, might) go to see my grandmother.
如果明天是星期天，我就（可能）去看我奶奶。
If it were to snow this evening, they would not go out.
如果今晚下雪，庄稼就一定（可能）有救。
4．主、从句的动作发生时间不一致的情况。
有时条件从句中的动作和主句中的动作发生的时间不一致，这时动词的形式要根据它所表示的时间加以调整。
If you had listened to the doctor, you would be all right now.
如果你当初听了医生的话，身体现在就好了。（从句动作指过去，主句动作指现在）
If you had practiced speaking English more, you would be able to speak it fluently.
如果你多练习讲英语，现在就能讲得很流利了。
（一）虚拟语气在主语从句中的用法
在“It is important (strange, natural, necessary) that…”这类句型里，that所引导的主语从句中的谓语动词常用“should＋动词原形”结构，表示某事“重要”、“奇怪”、“自然”、“必要”等意义。
It is important that every member (should) inform himself of these rules.
重要的是每个成员应知道这些规则。
It is necessary that he (should) be sent there at once.
有必要马上派他到那里去。
It is decided (has been decided) that the meeting (should) be postponed till tomorrow.
已决定会议延期到明天。
It is very strange that she (should) have left without saying goodbye.
她不辞而别，真让人奇怪。
（二）虚拟语气在宾语从句中的用法
1．wish后宾语从句中虚拟语气动词的时态意义
wish一般用来表达不能实现或没有把握实现的愿望，这种愿望是不真实的，所以其宾语从句动词用虚拟语气，译成汉语时可用“要是……就好了，但愿……”等。
（1）希望与wish时态同时发生的事，状态动词用过去式，动作动词用过去进行时，be在其主语是第一、三人称单数时多用were，少用was。这时，宾语从句所说的事实际上并不存在，只是说话人的一个愿望或遗憾。如：
I wish I knew more about the subject.
我(现在)要是对这门学科懂得多些就好了。
At that time how I wished I knew more about the subject.
那时我多么希望我对这门学科懂得多些啊。
How I wish it weren't raining .
我(现在)多么希望天(现在)不在下雨啊。
（2）希望在wish时态所体现的时间以前曾发生某事或曾存在某状态，动词用过去完成时形式，或情态动词＋have＋过去分词。这时，宾语从句所反映的事实际上未曾发生或不存在，它表达了说话人的遗憾。如：
He always wishes he had had some schooling so that he can make things clearer to us.
他经常想，要是他(过去)上过学多好，他可以把问题对我们讲得更清楚了。
Little Franz wished he had never wasted so much time in the woods.
小弗朗兹(过去)真希望他从未在树林里浪费那么多的时间。
I wish I could have been present at the meeting yesterday.
要是我昨天能出席会议就好了。
（3）希望在wish时态将来发生的事，用would＋动词原形。这时，表达了说话人对现在状况的不满和对将来所改进的愿望，但对这愿望的实现不抱太大希望，甚至完全不指望。如：
I wish it would stop raining soon.
但愿雨会停下来。
I wish the prices would go down.
但愿物价会下降。
There was so much beauty around us that we wished the journey would never end.
我们周围的风景真是美不胜收，我们真希望游程永远不会结束。
2．在suggest, demand, order, propose, insist, command, request, desire等动词后的宾语从句中谓语动词用“should＋动词原形（ should可省略）”，表示建议、要求、命令等。
I suggest that we (should) set off at once.
我建议马上动身。
I demand that he (should) answer me immediately.
我要求他立刻答复我。
The students insisted that they (should) have more English classes.
学生们坚持要多上英语课。
注意：上述动词转化或派生的名词以及idea, notion, no wonder, a shame, a pity等后的表语从句，表语从句、主语从句或同位语从句中也用(should +)动词原形，如：
Our decision is that the school remain closed.
It's a pity that he (should) call black white.
He made a request that the new electronic instrument (should) be tested at once.
（三）虚拟语气在状语从句中的用法
1．在有even if/ even though 引导的让步状语从句的主从复合句中主句和从句都用虚拟语气，动词形式与含有非真实条件句的虚拟语气相同。
Even if Lin Tao were here, I should say the same thing.
即使林涛在这儿，我也要这样说。
Even though he had been ill, he would have gone to his office.
即使生病了，他仍要去办公室。
当从句由though/although引导时，主句常用陈述语气，从句可用也可不用虚拟语气。
This gave me some faint hopes of relief, although I were (was ) not able to imagine how it could be brought out.
这给了我一线解救的希望，但我想象不出如何实现。
2．由as if 或as though引导的状语从句表示比较或方式时从句的谓语形式为动词过去式（be用were）或“had＋过去分词”。
He treats me as if I were a stranger.
他那样待我，好像我是陌生人似的。
She talked about the film as if she had really seen it.
她谈论那部影片，就好像好确实看过一样。
如果表示的事情可能会发生，那么方式状语从句中的谓语动词可用陈述语气。
3．在in order that 或so that引导的目的状语从句中谓语动词多用“could/might(有时也用should)＋动词原形”。
Mr. Green spoke slowly so that his students could/ might hear clearly.
格林先生说得很慢，好让学生听清楚。
They are climbing higher in order that they might/could get a better view.
他们正往更高处爬，以便看得更清楚。
在in case, for fear (that), lest 等引导的从句中，谓语动词用“should＋动词原形”。in case引导的从句还常用陈述语气，for fear (that) 引导的从句的谓语还可用情态动词may, might或would。
She took her raincoat with her in case/for fear that/lest she (should) be caught in the rain.
她带了雨衣，以免遭雨淋。
Remind me of it in case I (should ) forget.
提醒我一下，免得我忘了。
（四）虚拟语气在定语从句中的用法
在“It is time (that)…”句型中，定语从句的谓语动词常用虚拟语气表示将来，动词形式用过去式或“should＋动词原形（should不可省略）”，意思是“该做某事的时候了”。如：
It’s time we went should go to bed. 我们该上床睡觉了。
It’s (high) time we did our homework. 我们该做作业了。
（五）虚拟语气在简单句中的用法
1．情态动词的过去式用于现在时态时。
表示说话人谦虚、客气、有礼貌，或委婉的语气，常用于日常会话。
It would be better for you not to stay up too late. 你最好别太晚睡觉。
Would you be kind enough to open the door? 请你开门好吗？
2．在一些习惯表达中。
You’d better go now. 你最好现在就去。
I would rather not tell you. 我宁愿不告诉你。
3．用“may＋动词原形”表示“祝愿”、“但愿”。
此时may须置于句首（多用在正式文体中）。
May you be happy! 祝你快乐！
May good luck be yours. 祝你顺利！
4．用动词原形。
Long live the people! 人民万岁！
“Good bless you,”said the priest. 牧师说：“愿上帝保佑你。”
（六）虚拟条件句可以转换的形式
1．省略连词if
在书面语中，如果虚拟条件从句中有were, had或should, 可以省略if，把这几个词放到主语之前，构成主谓倒装。
Should he come (If he should come), tell him to ring me up.
他要是来了，让他给我打个电话。
Were I you (If I were you), I would not do it.
我要是你，就不做这事。
Had he been more careful (If he had been more careful), such mistakes could have been avoided.
如果他细心些，这些错误本来是可以避免的。
注意：在虚拟条件句中，省略连词的倒装形式，其句首不能用助动词的缩略否定式。如：
Were it not for the expense, I would go to Paris.
不能说成：Weren’t it for the expense, I would go to Paris.
2．用介词短语代替条件状语从句
有时假设的情况并不用条件从句表示出来，而是通过介词短语来表示。
Without air (If there were no air), there would be no living things.
如果没有空气的话，就不会有生物了。
But for your help (If it hadn’t been for your help) I couldn’t have done it.
要是没有你的帮助，我就不可能完成这件事。
假设的情况有时可以通过上下文或其他方式表现出来。
I was busy that day. Otherwise I would have gone there with them. (If I hadn’t been busy that day, I would have gone there with them.)
我那天很忙，否则，我就和他们一起去那儿了。（如果我那天不忙的话，我就……）
I would have finished the work, but I have been ill. (If I hadn’t been ill, I would have finished the work.)
我本来该完成这项工作的，但我生病了。（如果我没生病的话，我就会……）
（七）省略条件从句或主句的虚拟语气
表示虚拟语气的主句或从句有时可以省略，但其含义仍可以推知。
1．省略条件从句
You could have washed your clothes yourself.
你本可以自己洗衣服的。（省略了“If you had wanted to”事实是：你自己没洗衣服，因为你不想洗。）
2．省略主句（常用以表示愿望）
If my grandmother were with me!
如果我的祖母与我在一起多好啊！（事实是：祖母已去世。）
If only she had not left!
如果她没走就好了！（事实是：她已经走了。）
If only the wind would stop!
风要是停了该多好！（事实是：风停的可能性很小。）
