在同学们学习的过程中，我们对it is adj for sb to do sth这个句式无比纯熟。

但对于it is adj for sb to do sth就知之甚少，或者总也区分不清楚。

即使能分清楚，也是机械记忆，不了解其中的奥秘。

所以，本篇文章，就来梳理一下这个语法点。

It is important for us to study English.

这个句子中important不是形容us的，而是用来描述 to study English这件事的。

且

It做形式主语。所以，这句话可以变更为：To study English is important for us.

• important不是形容sb的，而是描述to do sth的
• 可以暂停形式主语it的职能，让不定式归位。

类似的形容词：difficult, easy, hard, important, dangerous, impossible

巧记：把id藏（hide）起来 hideid

H: hard

I:important

D: difficult

E: easy

I: impossible

D: dangerous

其实关于有哪些形容词是修饰不定式的，完全可以不去记忆。只要理解了这个形容词是形容人的还是形容事儿的就ok了。

更多例句：

It is very dangerous for children to cross the busy street.

= To cross the busy street is is very dangerous for children

≠ Children are dangerous to cross the busy street. (孩子不是危险人物，过马路危险)

It is difficult for children to pass the test.

= To pass the test is difficult for children.

≠ Children are difficult to pass the test. (孩子人不难，做题事儿难)

It is very kind of you to help me.

这个句子中，kind不是修饰to help me的，而是修饰人（you）的。

You are kind to help me.

有的同学，非常容易受到母语的干扰，狡辩如下：

帮助我是一件善良的事儿，是一种善良的行为。

我只能告诉你：你按照汉语逻辑，你可以任意翻译，只要有"帮助"、"善良"你就随便添加句义吧。

我们说英语，它是结构化的语言。汉语是表意化的语言。

结构化的意思是说：你必须按照这个结构去理解句义。

表意化的意思是说：句义的表达不受结构太大的限制。

所以，只要你用了of，这个kind就一定是修饰you的。

而且，英语里面的kind，是形容词，只能表示人的品质，它不能表示动作的属性。

错误举例：to help me is kind. 不能人为主观认为：助人为乐是善良的事儿。英语里只有人善良，事儿不能善良。

所以，能用of的形容词，都是形容人的品质的。包括这些：

Kind, good, nice, right, wrong, clever, careless, polite, foolish等等。

品质类形容词，字典里无穷无尽。

勇敢、胆小；

坚强、软弱；

聪明、蠢笨；

和善、虚伪；

勤劳、懒惰；

正直、阴险；

坦诚、狡诈

等等都是，所以具体形容词我们没有必要记忆，只要语文还可以，英语一定没问题。

更多例句:

It is clever of you to work out the problem.

= You are clever to work out the problem.

≠ To work out the problem is clever of you.

= To work out the problem can prove that you are clever.

It is brave of you to fight against the monster.

= You are brave to fight against the monster.

≠ To fight against the monster is brave of you.

= To fight against the monster can prove that you are brave.

Of：形容词说人

For：形容词说事儿

1. It is necessary_____ people to have food and water every day.

2.It's very convenient _____ us to buy train tickets now because we can buy them either from the station or on the Internet.

3.It's clever _____ you to make so many toy ships.

4.It's important _____ us to become polite in class.

5.It's careless _____ you to make lots of mistakes.

6.It's very nice _____ you to get me two tickets.

7.It's bad _____ you to eat too much junk food.

8.It's good _____ us to do exercise very day

答案：

for, for, of, for, of, of, for, for

good & bad：这俩词可以形容事儿，也可以形容人。

形容事儿的时候，相当于easy和difficult。

形容人的时候，相当于kind和rude

用心体会就好。

作者：王兴刚老师，前高校英语教师，现教育行业创业者，英语教学16年。本头条号的日常推文主要包括：关于教育问题的理解与感悟，关于英语知识的梳理和剖析，关于英语考点的讲解与总结。

该文同步发布于本人微信公众号（王兴刚老师）。