說文解字 （23）：不需加上 TO 的不定詞  

說到不定詞 infinitive, 我們通常會想到在動詞前加 上TO變成不定詞； 其實， 不定詞在下列不同句型中可加也可不加 「TO」出現。

 1. 句中第一個(主）動詞後的每一個動詞前加上 TO使他們變成不定詞， 如下例：

He goes there to take a walk, to exercise and to socialize with friends.  To see is to believe. She eats to live, not lives to eat.

 2. 句中助動詞後的每一個動詞前不必加TO，但他們不失為不定詞， 見下例：

I can design a plan and he will implement it. I don’t know, she does not know either. They will/would arrive by noontime. She must have done it.

 The father helps the son carry his luggage.

I watched the tree fall on that car.

She needs not finish this job today.

The teacher let Mary go home early after she had finished the assignment.

I saw him jump into the lake.

The father noticed his son work with confidence..

I heard Mary sing an old song.

What made you think he is a good guy.

I feel someone touch my pocket.

4. 下面是另類不用加 TO 的不定詞用法。

 He had better finish his homework before his father comes home.

He would rather die than lose freedom.

從上面句例中， 我們可以改變 不定詞中必須有TO的刻板印象， 還有， 不管句中的主動詞是甚麼時式， 其有關的不定詞一律用動詞的原式， 即使在第三人稱單數現在式的句中的不定詞， 也不必加  [S] 或 「ES].

感謝格友Apple Blossom提供有關不定詞更多的資料， 她 所給的網址和評語：