"to + 原形動詞"   所形成的名詞不定詞可當作名詞看待.

a. 名詞不定詞當主詞:

用於表示一種意願或未完成的事.

例:

To marry her is my goal.

To win the championship is my ambition.

b.名詞不定詞當及物動詞的受詞

例:

I want to see him.

He intends to try it.

c.名詞不定詞在be動詞後作主詞補語

例:

To see is to believe.

To love her this way is to worship her.