§ Some Uses of Infinitive

不定詞或不定詞短語跟某些單詞連用，有特殊的意義。 

1. 表示「能夠」
    
    形態：be + able + infinitive

例如：

  I can speak English.
  I am able to speak English.
  I cannot speak English.
  I am not able to speak English.
  I am unable to speak English.

  I could speak English last year.
  I was able to speak English last year.
  I could not speak English last year.
  I was not able to speak English last year.
  I was unable to speak English last year.

※ "can + root form" 和 "could + root form" 只能表示
   一般現在時態及一般過去時態，其他時態就不能表示了。
   若要表示，就要用 "be + able + infinitive"。例如：
         
  When shall I be able to speak English?

  You will be able to speak English next year.

  Has your baby been able to walk by himself now?

2. 表示「必須」
         
    形態：have + infinitive

例如：

  You must go.
  You have to go.

  * "have to" 好比 "must"。

※ "must + root form" 只能表示一般現在時態及一般過去時態，
   其他時態就不能表示了。
   若要表示，就要用 "have + to + infinitive"。例如：

  You had to go to school yesterday.

  * "had to" 好比 "must" 的一般過去時態。

  You will have to serve in the army next year.

  You have had to go to school now. Why are you still 
  playing ball here?

  * "have had to" 表示現在完成時態。

3. 表示「從﹝何處﹞做﹝什麼﹞回來」
         
    形態：have been + to (place) + infinitive

例如：

  I have been to Kowloon Bay to visit my grandmother.
  ﹝我從九龍灣探訪我的祖母回來。﹞

  I have been to the airport to see my friend off.
  ﹝我從機場送我朋友的機回來。﹞

4. 表示「安排好的將來」
         
    形態：be + infinitive

例如：

  I am to go to the movies tonight.

  We are to be married in May.

5. 表示「快將發生的將來」

    形態：be + going + infinitive

例如：

  It is going to rain soon.

  He is going to leave tomorrow.

6. 表示「即將發生的將來」
         
    形態：be + about + infinitive

例如：

  The plane is about to start.

  I am about to resign my position.

  * "be going to" 和 "be about to" 都有「快將」或「即將」之意。
    前者較口語，多用於日常會話中；後者較文言，多用於文章中。

※ 表示「將來」的說法有多種：

 1. I study English tomorrow.
    ﹝用 Simple Present Tense加上表示將來的副詞表示。﹞

 2. I shall study English.
    ﹝表示純粹的將來。﹞

 3. I will study English.
    ﹝表示「主角意願」的將來。﹞

 4. I am to study English.
    ﹝表示安排好的將來。﹞

 5. I am going to study English.
    ﹝表示快將發生的將來。﹞

 6. I am about to study English.
    ﹝表示即將發生的將來。﹞

練習

翻譯

1. 你的弟能繪畫嗎？
2. 你必須學習英文文法。
3. 我安排明年赴美國學習數學。
4. 你十六歲那年，你必須供養你的妹妹嗎？
5. 我昨天不能幫助你，但今天我能幫助你了。
6. 他的兒子明年能夠寫流暢的信了。
7. 因為我病了，你必須立刻通知他們我不能去了。
8. 他的父親快將起程赴星加坡。
9. 他即將探訪他的姑媽嗎？
10. 我從書局買了一些書回來。