什么是时态：时间+状态
先来感受一下时态~
1. I just feel hopeless. I can't do enough. My children wanted me. They needed me. And now I can't help them. I just feel like such a failure. (Blind-Sided: Homicide Where It Is Least Expected)
句子中的一般过去时，表示这位母亲知道孩子已经去世。对比，有些走失儿童的父母，在表达这是孩子的房间时，会用一般现在时，内心认为孩子还活着。
2. 试比较：（注意语境不同另当别论）
He is an English teacher. 他现在是一名英语老师。
He was an English teacher. 他生前是一名英语老师。（was表示人去世）
He used to be an English teacher. 他曾是一名英语老师。（现在可能不是）
时态要如何用
一般现在时的用法：2个
1. 表达现在的情况、状态的用法
Monica Lewinsky: There is absolutely no sex of any kind in any manner shape or form with president Clinton.
President Clinton: There is no improper relationship.
克林顿总统针对桃色丑闻的辩词：It depends upon what the meaning of the word "is" is.
1） If "is" means "is and never has been", that is not——that is one thing（现在且以前没有，说谎了）
2） If it means "there is none", that was a completely true statement.（说话的那个时候没有，没说谎）
2. 超越自然时间的用法
She always takes a walk in the evening. (习惯、反复动作)
Water boils at 100℃（真理、事实）
I declare the meeting open（现在、瞬间）
I hear Brotherfive has come back from America.（表过去）
Tomorrow is Christmas Day（表将来）
The plane takes off at eight and arrives in Beijing at eleven（表将来）
表示说明介绍
U.S. President holds talks with British Prime Minister.（新闻）
I Have a Chance（小说的章标题）
At rise, the stage is dark. It is two thirty in the morning. （舞台说明）
The contracts holds good. 合同有效
现在进行时的用法
1. 表示进行的动作或正在发生的事
2. 表示非延续性或反复性的动作
（1）表示某个按最近的计划或安排，将要进行的动作，或即将开始或结束的动作
go, leave, come, arrive, land meet, move, return, start, stay
do, dine, give, have, pay join, punish, spend, sleep, take
change, fly, work, wear, see launch, play
栗子：He is meeting Brotherfive tomorrow. 他明天要和武哥见面
（2）动作动词的进行时与always, forever, continually, constantly等连用，表示重复的动作，这种动作可能使人感到厌倦或觉得不合理，有时表示赞赏、满意
Students are always doubting the sample translation offered by Brotherfive.
（3）系动词be的进行时+动态形容词，表示暂时出现的某种情况或品质。
You are being foolish. 你在办蠢事（平时不糊涂）
（4）某些短暂性动词也不可用于进行时，常见动词有：
admit, decide, end, allow, refuse consent(答应), permit, receive, determine, resolve
deny, promise, accept, complete
例子：He is denying that he has seen the wallet. (is denying改为denies)
（5）表示反复多次或习惯性动作
Brotherfive is nodding his head. 武哥频频点头（nod是短暂性动词，进行时表示反复多次）
现在完成时用法
1. 影响性用法（事情发生且结束，产生结果影响到现在）
Although（看见这个词，找主句） surveys of /medieval legislation, guild organization and terminology used（后置定语） to designate different medical practitioners/ have demonstrated that /numerous medical specialties were recognized in Europe during the Middle Ages, /most historians continue to equate the term "woman medical practitioner", wherever they encounter it in medieval records with "midwife".
2. 延续性用法
Brotherfive has been in this line of business for more than 20 years.（从过去，延续到现在）
since用法：
since表示自从...，从句多用短暂性动词，主句一般用完成时态，如果用延续性用词或静态动词的过去式，所表示的就是动作或状态的完成或结束
Since he left Nanjing last year, i haven't heard from him.自从他去年离开南京，我就没有收到过他的信。
Since he lived in Nanjing, I have not heard from him. (=Since he left Nanjing...)
She has written to me frequently since i was ill.（自从我病愈以来）
3. 特殊句型用法
（1）在after, as soon as, if, till, when等引导的状语从句中，用现在完成时，代替将来完成时或一般现在时
I shall go to see you when i have finished my homework.
How can i concentrate if you have continually interrupting me with silly questions?
（2）It/This is the first (last, second, third...) time that...结构中的that从句要求用现在完成时。
It/This is the second time that we've met each other. 这是我们第二次见面了。
（3）It/This is the best(worst, most interesting) +n +that...结构中的that从句要求用现在完成时
This is the most interesting novel he has ever written. 这是他所写的最有趣的一部小说。
以上内容根据大春老师网课整理
