o和ao的用法上如何区别 没和无在用法上有何区别？

没和无在用法上有何区别？  

没和无在用法上有何区别？

没和无表示的含义不一样，没是一种含否定语气的意思，不具备拥有与否的意思，而无，则是有拥有的含义在里面，是不拥有的意思。没有等于无，没不等于无。

since和for在用法上有何区别

很高兴回答你的问题，以下是我个人见解，希望可以帮到你：
since+时间点
for+时间段
Since 用来说明动作起始时间,for用来说明动作延续时间长度.
since的用法主要有两点：一是表示“自从……以来”,二是表示“既然”之意.但如果只了解词的含义,而不了解其用法,在使用时就会造成错误.例如：I have not heard from him since I lived in Shanghai.
不少人会望文生义,将该句译为：“自从我住在上海以来,就再也没有收到他的信了.”而实际上这个句子的译文并非如此,那么正确的含义是什么呢?
下面谈谈since作连词引导时间状语从句的用法.
一、若since引导的状语从句的谓语动词是终止性的过去时,则从句表示的时间是“从动作开始的那一时刻起”.如：
He has studied very hard since he came to our school.自从他来到我们学校,他学习就非常努力.
We have been missing them since they left here自从他们离开这里,我们就一直很想念他们.
这是最常见的一种用法,此处不再多述.
二、若since引导的状语从句的谓语动词是持续性动词或表示状态的动词的过去时时,则从句表示的时间是“从那持续动作或状态结束时算起”.如：
I haven’t heard any noise since I slept. Sleep 为持续性动词,sleep的动作结束时,即“醒来”时,这句应译为“我醒后还未听到任何声音”.
John is now with his parents in New York, it is already three years since he was a teacher约翰现在和父母一起住在纽约,他不当教师已经三年了.
本文开始出现的那个句子就可以译为“自从我离开上海,就再也没有收到他的信.”这种译法常被人们误用,我们不妨再多举几个例子看看：
How long is it since you lived in Shanghai?你离开（没住在）上海多久了?
It is half a month since he was a League member.他退团（不当团员）半个月了.
It’s been quite some time since I was last in London我离开伦敦已很长时间了.
比较：He has written to me frequently since I was ill.自从我病愈以来,他屡次给我写信.（从句谓语为状态动词）
He has written to me frequently since I fell ill.自从我生病以来,他就屡次给我写信.（从句谓语为终止性动词）
三、若since引导的状语从句的谓语为持续性动词的现在完成时,则表示动作和状态延续到现在（说话时刻）,其表示的时间的起点应从动作发生之时算起.如：
I haven’t heard from him since he has lived there.
这里has lived表示动作的持续性,时间的起点应从：“开始居住”时算起.因此此句可理解为“自从他（开始）住在那儿起,我就一直没收到他的来信”.
Since we have owned a car, we have gone camping every year.自从我们自己有了汽车,我们每年都去野营.
试比较：1. Since I’ve been at this school, we have had three headmasters.自从我到这所学校,我们已换了三个校长了.
Since I was at this school, they have had three headmasters.自从我离开这所学校,他们已换了三个校长了.
2.He has never been to see me since I have been ill. 自从我生病以来,他从未来看过我.
He has never been to see me since I was ill. 自从我病愈以来,他从未来看过我.
由此可见,since引导的从句持续动词的一般过去时和现在完成时所表示的意思恰好相反.换言之,前者以肯定的语法形式反映着否定的逻辑内容,而后者的形式与内容是一致的.
至于It is +一段时间+since…的句型与It has been +一段时间+since…意思相同.前者是规范说法,后者是口语说法.
应注意的是,在这种结构中,since引导的从句绝对不能用否定式的谓语动词来表示否定意义,下面两句都错了：
It is a long time since he didn’t study English.
It’s o months since you didn’t e to see me.
正确的说法为：
It’s a long time since he studied English 他好久没学英语了.
You haven’t e to see me for o months. 你有两个月没来看我了.
一、延续性动词和终止性动词的概念
英语中,动词按其动作发生的方式、动作发生过程的长短,可分为延续性动词和终止性动词.
延续性动词表示能够延续的动作,这种动作可以延续下去或产生持久影响.如：learn, work, stand, lie, know, walk, keep, have, wait, watch, sing, read, sleep, live, stay等.
终止性动词也称非延续性动词、瞬间动词或短暂性动词,表示不能延续的动作,这种动作发生后立即结束.如open, close, finish, begin, e, go, arrive, reach, get to, leave, move, borrow,buy等.
二、延续性动词的用法特征
1.延续性动词可以用于现在完成时,其完成时态可与表示"段时间"的状语连用.表示"段时间"的短语有：for o years, during the past three years, since last year, how long等.如：I have learned English since I came here.自从我来到这儿就学英语了.
2.延续性动词不能与表示短暂时间的"点时间"状语连用.如：It raind at eight yesterday morning.(误) rain为延续性动词,而at eight表示"点时间",前后显然矛盾.如果用延续性动词表示一瞬间的动作,可以借助e, begin, get等终止性动词来表示.上句可改为：It began to rain at eight yesterday morning.(正)又如：
-When did you get to know Jack?
-Two years ago.
-Then you've known each other for more than o years.
-That's right.
三、终止性动词的用法特征
1.终止性动词可用来表示某一动作完成,因此可用于现在完成时.如：
The train has arrived.火车到了.
Have you joined the puter group?你加入电脑小组了吗?
2.终止性动词表示的动作极其短暂,不能持续.因此,不可与表示一段时间的状语连用(只限肯定式).如：
(1)他死了三年了.
误：He has died for three years.
正：He has been dead for three years.
正：He died three years ago.
正：It is three years since he died.
正：Three years has passed since he died.
(2)他来这儿五天了.
误：He has e here for five days.
正：He has been here for five days.
正：He came here five days ago.
正：It is five days since he came here.
正：Five days has passed since he came here.
(1)、(2)句中的die、e为终止性动词,不能与表示"段时间"的状语连用.那么,应如何正确表达呢?可以采用下面的四种方法：
(1)将句中终止性动词转换为相应的延续性动词,如上面两例中的第一种正确表达方式.下面列举几例：leave→be away, borrow→keep, buy→have, begin/start→be on, die→be dead, move to→live in, finish→be over, join→be in/be a member of, open sth.→keep sth. open, fall ill→be ill, get up→be up, catch a cold→have a cold.
(2)将句中表示"段时间"的状语改为表示过去确定时间的状语,如下面两例中的第二种正确表达方式.
(3)用句型"It is+段时间+since..."表达原意,如上面两例中的第三种正确表达方式.
(4)用句型"时间+has passed+since..."表达原意,如上面两例中的第四种正确表达方式.
3.终止性动词可用于现在完成时否定式中,成为可以延续的状态,因而可与表示一段时间的状语连用.如：
He hasn't left here since 1986.
I haven't heard from my father for o weeks.
4.终止性动词的否定式与until/till连用,构成"not+终止性动词+until/till ..."的句型,意为"直到……才……".如：
You can't leave here until I arrive.直到我到了,你才能离开这里.
I will not go to bed until I finish drawing the picture tonight.今天晚上直到我画完画,我才上床睡觉.
5.终止性动词可以用于when引导的时间状语从句中,但不可以用于while引导的时间状语从句中.when表示的时间是"点时间"(从句谓语动词用终止性动词),也可以是"段时间"(从句谓语动词用延续性动词).而while表示的是一个较长的时间或过程,从句谓语动词用延续性动词.如：
When we reached London, it was elve o'clock. (reach为终止性动词)
Please look after my daughter while/when we are away. (be away为延续性动词短语)
6.终止性动词完成时不可与how long连用(只限于肯定式).如：
误：How long have you e here?
正：How long have you been here?
正：When did you e here?
望采纳，十分感谢。

till和until在用法上有何区别？

till / until在表达方式和意义上的特殊性：until是till的强调形式，但是它们表达的意义是相同的，都表示"直到某时"。不过，当主句是否定句时，它引出的意思是"直到（某时）（某动作）才（发生）" ，这时候常会出现"not until …"的结构，如果将 "not until …"的结构放在句首，那么主句要写成倒装句。例如：
He didn't go to sleep until 12 last night .
他昨晚直到十二点钟才睡觉。
They didn't realize their fault till we pointed it out to them .
直到我们向他们指出了他们的错误，他们才意识到。
Not until we pointed out their fault to them did they realize it .
直到我们向他们指出了他们的错误，他们才意识到。
但是，当主句是肯定句时，它引出的意思是"直到（某时某动作停止了）" 。例如：
The students made much noise till the teacher came into the classroom .
直到老师走进教室学生们才停止了大声喧譁。
The young couple were very happy until they used up all their money .
那对年青夫妇直到花光了所有的钱才沮丧起来。
另外，until 可以放在句首而till则不行。我们可以说：Until they used up all their money, the young couple were very happy .我们却不可以说：Till they used up all their money, the young couple were very happy .
此两个连词意义相同。肯定形式表示的意思是"做某事直至某时"，动词必须是延续性的。否定形式表达的意思是"直至某时才做某事"。动词为延续性或非延续性都可 以。 正确使用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。

肯定句：
I slept until midnight. 我一直睡到半夜时醒了。
Wait till I call you. 等着我叫你。
（在肯定句中可用before代替 Let's get in the wheat before the sun sets.）

否定句：
She didn't arrive until 6 o'clock.
她直到6点才到。
Don't get off the bus until it has sped.
公共汽车停稳后再下车。
I didn't manage to do it until you had explained how. 直到你教我后，我才会做。
1)Until可用于句首，而till通常不用于句首。
Until you told me, I had heard nothing of what happened.
直到你告诉我以前，出了什么事我一点也不知道。
2)Until when 疑问句中，until要放在句首。
---Until when are you staying? 你呆到什么时候？
--- Until next Monday. 呆到下周一。
注意：否定句可用另外两种句式表示。
(1）Not until …在句首，主句用倒装。
Not until the early years of the 19th century did man know what heat is.
直到19 世纪初，人类才知道热能是什么。
Not until I began to work did I realize how much time I had wasted.
直到我开始工作，我才认识到了我已蹉跎了几多岁月。
(2) It is not until… that…

confidential和secret在用法上有何区别

confidential 多形容档案，特别是国家，私人企业机关的档案，资讯secret 常出现在口语里，形容个人事情的祕密性。

by taxi 和take taxi 在用法上有何区别？

by是介词，take是动词楼上说得没错，by后面不加冠词。区别就是take是动词可以放在主语或宾语后面比如I take a taxi to school.而不能说I by taxi to school.

heaven和paradise在用法上有何区别?

heaven天堂，天国。顾名思义在天上
paradise乐园，可以在地上呀，如Eden

during、while在用法上有何区别

when和while的区别
①when是at or during the time that, 既指时间点，也可指一段时间；
while是during the time that，只指一段时间，因此when引导的时间状语从句中的动词可以是终止性动词，也可以是延续性动词，而while从句中的动词必须是延续性动词。
②when 说明从句的动作和主句的动作可以是同时，也可以是先后发生；while 则强调主句的动作在从句动作的发生的过程中或主从句两个动作同时发生。
③由when引导的时间状语从句，主句用过去进行时，从句应用一般过去时；如果从句和主句的动作同时发生，两句都用过去进行时的时候，多用while引导，如：
a. When the teacher came in, we were talking.
当此句改变主从句的位置时，则为：
While we were talking, the teacher came in.
b. They were singing while we were dancing.
④when和while 还可作并列连词。when表示“在那时”；while表示“而，却”，表对照关系。如：
a. The children were running to move the bag of rice when they heard the sound of a motor bike.
孩子们正要跑过去搬开那袋米，这时他们听到了摩托车的声音。
b. He is strong while his brother is weak.
他长得很结实，而他弟弟却很瘦弱。
具体你可以参考这一段。
when，while，as引导时间状语从句的区别
when，while，as显然都可以引导时间状语从句，但用法区别非常大。
一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。
① Why do you want a new job when youve got such a good one already？（get为短暂性动词）你已经找到如此好的工作，为何还想再找新的？
②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外出了。
③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。
④ The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。
二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓语动作必须是和主句谓语动作同时发生。
1．从句动作在主句动作前发生，只用 when。
①When he had finished his homework，he took a short rest．（finished先发生）当他完成作业后，他休息了一会儿。
②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。
2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。
①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。
②When ／While ／As she was making a phonecall，I was writing a letter．（make为延续性动词）当她在打电话时，我正在写信。
3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背景或条件时，只能用 as。这时，as常表示“随着……”；“一边……，一边……”之意。
① As the time went on，the weather got worse．（as表示“随着……”之意）
② The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来越稀薄。
③As years go by，China is getting stronger and richer．随着时间一年一年过去，中国变得越来越富强了。
④The little girls sang as they went．小姑娘们一边走，一边唱。
⑤The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边叫。
4．在将来时从句中，常用when，且从句须用一般时代替将来时。
①You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。
②When the manager es here for a visit next week，Ill talk with him about this．下周，经理来这参观时，我会和他谈谈此事。
三、when用于表示“一……就……”的句型中（指过去的事情）。
sb．had hardly（＝scarcely） done sth．when．．．＝Hardly ／ Scarcely had sb．done sth．when．．．
①I had hardly ／scarcely closed my eyes when someone knocked at the door．＝Hardly ／ Scarcely had I closed my eyes when someone knocked at the door．我刚一闭上眼，就有人在敲门了。
②I had hardly ／scarcely entered my room when the telephone rang．＝Hardly ／Scarcely had I entered my room when the telephone rang．我刚一走进房门，电话就响了。

can i和may i 在用法上有何区别？

can 是表示能力，表示获得的知识或者技能，通常可以与感官动词连用。可以表示许可，要求，以及可能性。
例如：Can he cook?他会做饭吗？（can在这里做能力解释）
Can I read your newspaper?我能看看你的报纸吗？（can 在这里做询问，表示要求）
may表示允许，许可。也可以用来表达可能。还可以用来表达愿望和希望。
例如： May I e in? 我能进来吗？（may在这里就是做询问，请求的意思）
一般来说can 的程度比may 要强烈一些。
而且一般在正式场合用may会感觉比较礼貌一些。

had a fever 和 got a fever在用法上有何区别

have a fever 强调的是一种状态延续性的。 I had a fever last week。

get a fever强调的是动作，也就是指短暂性的。I got a fever after walking in the rain。

但是我觉得这两个没有什么太大的区别啦，用法上不必太较真。

understand与prehend在用法上有何区别

prehend:侧重熟悉了解的过程.
understand:指对事物已有彻底的认识,不仅知其性质、含义和细节,而且了解其内外的关系.