'I have eaten' is the present perfect tense of the verb 'to eat', 'I had eaten' is the past perfect and 'I will have eaten' is the future perfect.
Ihave eaten是动词eat的现在完成时；Ihad eaten是过去完成时；Iwill have eaten是将来完成时。
The present perfect is covered in Unit 8.
现在完成时在第8单元讲解。
When you ask about something that started in the past but continues to the present time, you use the Present Perfect tense, e.g.: I’ve been there for 5 years / I’ve been there for 5 years.
当你谈论在过去开始但是一直持续到现在的某事时，用现在完成时态，例如：I’vebeentherefor5years/我在那里已经5年了。
When we use the present perfect, there is a connection with now.
当我们使用现在完成式时，是和现在有关联的。
Rewrite the following sentences using the present perfect passive voice.
用现在完成时的被动语态改写下列句子。
The present perfect is almost a kind of present tense.
现在完成时总是一类现在时态。
If we say when a past event happened (for example, by using time-adverbs), we do not usually use the present perfect.
说过去发生的事件(例如：用过去时间状语)，我们通常不用现在完成时。
We use the present perfect tense to talk about something that happened at an indefinite time in the past.
我们使用现在完成时谈论发生在过去某个不确定的时间的事情。
We use the present perfect tense to talk about things that started in the past and still have some connection with the present.
我们用现在完成时来谈论在过去开始并且仍与现在有联系的事情。
When we talk about past events which have no present importance, we do not use the present perfect.
谈论过去的事件其对现在不重要，不用现在完成时。
When we want to talk about actions or situations which started in the past and have continued up to the present, we often use the present perfect to show the connection between past and present.
要谈论行为或状态其始于过去而持续到现在，经常使用现在完成时表现过去和现在之间的连接。
At first glance it looks as if there is no element of "present involvement" in this use of the present perfect any more than in the simple past.
乍看起来，在现在完成时的用法中，似乎跟在一般过去时中一样，都没有“涉及现在”的因素。
You'll notice that's its very common for a native speaker to use the present perfect continuous like this when greeting a buddy.
你会发现对于一个母语使用者，他们在问候兄弟时很喜欢用现在完成进行时。
For example, try to write down each example of a form you are studying such as the present perfect.
比如，列出你正在学的语法知识的全部形式，如现在完成时。
So you learn the past tense and then two or three weeks later, oh now you are learning the present perfect, and then a few weeks later, you are learning the future, that's crazy.
你学习了过去时，然后两到三周后你开始学习现在完成时，几周以后你又开始学习将来时，这简直太疯狂了。
To grasp the usage of the present perfect tense.
掌握现在完成时态的用法。
You'll be able to use the present perfect tense for checking up.
你可以用现在进行时态去检查。
When we make a present perfect sentence, we could usually make a present tense sentence about the same situation.
造现在完成时的句子，我们通常会造现在时态的句子。
Fill in the blanks with the present perfect tense of the verbs in brackets.
用括号里动词的现在完成时态来填充空格。
I have finished 'is an example of the present perfect.
“我已经完成了”是现在完成时态的一个例句。
In this lesson, we will practice using the present perfect tense.
在这节课上，我们将要练习使用现在完成式。
The present perfect is used to express an action that started in the past but still continues in the present.
现在完成时用来表达开始于过去但仍在现在持续的动作。
Change these sentences into the present perfect passive putting the verbs into the correct forms.
用动词的正确形式将下面的句子变成现在完成时的被动语态。
The present perfect tense emphasizes the effect of the past action on the present.
现在完成式强调过去所发生的事情对现在的影响。
We also use the present perfect to talk about repeated actions in the past.
我们还使用此时态谈论过去重复的动作。
We also use the present perfect to talk about repeated actions in the past.
我们还使用此时态谈论过去重复的动作。
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