现在完成时结构
现在完成时的构成：
陈述句：S（主语）+ have/ has + 动词过去分词
I have had dinner.
否定形式：S（主语）+ hasn't/haven't + 动词的过去分词
I haven’t had dinner.
疑问形式：Have/has + S(主语) +动词过去分词
Have you had dinner?
肯定回答：Yes, S(主语)+ have/ has.
否定回答：No, S（主语）+ have/ has+ not.
现在完成时适用范围：
1、谈论过去发生的事情，但是发生的时间不重要.
e.g. She has broken her arm. 她伤了她的胳膊.
2、谈论过去发生的某事，但对现在造成了影响
e.g. She has broken her arm, so she can’t play basketball.
她伤了她的胳膊, 所以她不能打篮球了.
3、过去开始的某事，现在还在继续.
e.g. He has lived in China for 20 years.
他已经在中国住了20年了.
He has lived in China since 1993.
4. 刚刚发生的事情.
e.g. They have just arrived at the airport. 他们刚刚到达了机场.
5. 经历或取得的成就.
e.g. He has passed his math exam with a high mark.
他以高分通过了他的数学考试.
现在完成时态中的重要标志词 already, yet, just, never, ever用法区别
1、 already意思是―已经‖
A、通常用于陈述句中（放在have和has的后面）
B、也可用于疑问句，表示期望得到肯定的回答或表示惊异，此时
already常放在句末。
She has already found her bike.
Has she found her bike already？她已经找到自行车了？
2、yet用法
A、yet可用于否定句，此时译为―还‖；
I haven’t found my ruler yet.
B、也可以用于疑问句，译为―已经‖（放在have和has的后面也可放在句末）
Have you found your ruler yet？你已经找到尺子了吗？
3、just只用于陈述句意思是―刚才‖（放在have和has的后面）
I have just received a letter.
4、never用于否定句译为―从不‖（放在have和has的后面）
I’ve never been to Beijing.
5、ever用于疑问句译为―曾经‖（放在have和has的后面）
Have you ever been to Beijing?
规则动词过去分词和过去式变法一样
1、一般情况在词尾+ ed clean --- cleaned
2、以不发音的e结尾的词+ d arrive --- arrived
3. 辅音字母+y结尾的去y加ied empty --- emptied
4. 双写最后一个辅音字母加ed stop --- stopped
不规则动词的过去式以及过去分词巧记规律
1、A: put–put–put let-let–let
2、ABA: come—came—come
3、ABB: stand—stood—stood
4、ABC: eat— ate—eaten
AAA：cost-cost-cost read-read-read
put-put-put cut-cut-cut
let-let-let set-set-set
AAA变化的单词，结尾字母一般是t或d。
特殊：动词read, 变化是read-read-read，但发音分别是[ri:d]-[red]-[red]。
ABA：有些动词的过去分词与原形是一样的:
run-ran-run
come-came-come
become-became-become
ABC：
ABC有些动词的过去分词是在原形词尾加n或en，变成以en结尾的单词。 take-took-taken give-gave-given
fall-fell-fallen eat-ate-eaten
write-wrote-written speak-spoke-spoken
forget-forgot-forgotten (forgot)
特殊情况
am/is-was-been are-were-been,
do (does)-did-done go-went-gone
see-saw-seen