现在完成时
现在完成时的构成
任何动词的现在完成时都是以两个要素构成：依人称使用正确的助动词 to have（现在时）的型态，加上主要动词的过去分词。规则动词的过去分词为动词原型 + ed，例如 played丶arrived丶looked。至於不规则动词，请参考「动词」页面上的不规则动词表。
| 肯定句 | ||
| 主词 | to have | 过去分词 |
| She | has | visited. |
| 否定句 | ||
| 主词 | to have + not | 过去分词 |
| She | has not (hasn't) | visited. |
| 疑问句 | ||
| to have | 主词 | 过去分词 |
| Has | she | visited? |
| 否定型疑问句 | ||
| to have + not | 主词 | 过去分词 |
| Hasn't | she | visited? |
现在完成时，以 to walk 为例
| 肯定句 | 否定句 | 疑问句 |
|---|---|---|
| I have walked. | I haven't walked. | Have I walked? |
| You have walked. | You haven't walked. | Have you walked? |
| He, she, it has walked. | He, she, hasn't walked. | Has he, she, it walked? |
| We have walked. | We haven't walked. | Have we walked? |
| You have walked. | You haven't walked. | Have you walked? |
| They have walked. | They haven't walked. | Have they walked? |
现在完成时的作用
现在完成时是用来表明现在与过去的连结。动作的时间是在过去，并没有一个具体的时间点。我们往往更强调动作的结果，而非动作本身。
要留意！也许您的母语中也有相似的动词时态，但意思不见得是一样的。
现在完成时是用来描述：
- 始於过去的动作或状态，到目前仍持续着。I have lived in Bristol since 1984 (= 而且到现在还是。)
- 在一段时间内做过丶但还没有结束的动作。She has been to the cinema twice this week (= 而且这周还没过完。)
- 在过去到现在之间的一段不明确的时间内重复发生的动作。We have visited Portugal several times.
- 在不久前完成的动作，以「just」来表达。I have just finished my work.
- 发生时间并不重要的动作。He has read 'War and Peace'. (= 阅读的结果很重要)
注意：如果想要针对何时丶何地丶何人给予或询问细节，我们会用过去简单时。关於这方面可以参考这篇文章，了解如何在现在完成时和一般过去时之间做选择。
始於过去且目前持续在做的动作
- They haven't lived here for years.
- She has worked in the bank for five years.
- We have had the same car for ten years.
- Have you played the piano since you were a child?
当提及的时间点还没结束
- I have worked hard this week.
- It has rained a lot this year.
- We haven't seen her today.
在过去到现在之间不具体的时间范围内重复做的动作
- They have seen that film six times
- It has happened several times already.
- She has visited them frequently.
- We have eaten at that restaurant many times.
刚结束的动作（加 just）
- Have you just finished work?
- I have just eaten.
- We have just seen her.
- Has he just left?
当动作的确切时间并不重要或未知时
- Someone has eaten my soup!
- Have you seen 'Gone with the Wind'?
- She's studied Japanese, Russian, and English.
进一步了解如何在现在完成时中使用 ever丶never丶already 和 yet，以及在现在完成时中使用 for 和 since。