It 形式主语 Formal Subject It
考试：📙 PET ✓ 📕 FCE·雅思 ✓ 中考 ✓ 高考 ✓ 分类：句型结构 考试入口：PET语法清单 | FCE·雅思语法清单 关联：代词 Pronouns | 宾语从句 Object Clauses | 不定式与动名词 Gerunds & Infinitives
核心规则（Grammar Core）
为什么要用 It 形式主语？
英语有个习惯：不喜欢把太长的东西放在句首（重心后置原则）。
To learn a language takes years. ← 主语太长，前置显笨重
It takes years to learn a language. ← it 占位，真正主语移到后面，更自然
It 是形式主语（Formal/Dummy Subject）——它自己没有意义，只是给句子一个主语占位，真正的主语在后面。
四大句型公式
| 公式 | 例句 |
|---|---|
| It + be + 形容词 + to do | It is important to study every day. |
| It + be + 形容词 + that + 从句 | It is surprising that she passed. |
| It + takes + (sb) + 时间 + to do | It takes me 30 minutes to get to school. |
| It + seems/appears/looks + (that) + 从句 | It seems that no one noticed. |
常见形容词搭配
| It + be + ___ | 例句 |
|---|---|
| important / essential | It is important to listen carefully. |
| difficult / hard / easy | It is hard to say goodbye. |
| possible / impossible | It is impossible to finish in one day. |
| necessary | It is necessary to bring ID. |
| clear / obvious | It is clear that she is right. |
| surprising / amazing | It is surprising that he knew. |
| true / false | It is true that English is widely spoken. |
| a pity / a shame | It is a pity that you can’t come. |
| a pleasure | It is a pleasure to meet you. |
| no use / no good | It is no use crying over spilt milk. |
| worth | It is worth visiting. |
It takes + 时间（重要句型）
| 结构 | 例句 |
|---|---|
| It takes + 时间 + to do | It takes two hours to drive there. |
| It takes + sb + 时间 + to do | It takes me two hours to drive there. |
| It took + 时间 + to do（过去） | It took three years to build the bridge. |
Grammar Lens
对比辨析：形式主语 vs 指示代词 it ⚠️
同一个 it，两种不同用法
类型 例句 it 指代什么 指示代词 I bought a book. It is very interesting. it = 那本书 形式主语 It is interesting to read this book. it 什么都不指，只是占位 判断技巧：把 it 换成后面的真正主语，能说通就是形式主语： “It is interesting to read.” → “To read is interesting.” ✅ = 形式主语 “It is very interesting.” → “The book is very interesting.” ✅ = 指示代词（需要上文）
It + be + adj + to do vs It + be + adj + that ⚠️
| 结构 | 强调 | 例句 |
|---|---|---|
| to do | 动作本身（做什么） | It is wrong to cheat. |
| that 从句 | 某个事实（某事是这样） | It is clear that he cheated. |
It is important TO STUDY English. ← 学英语这件事很重要（行为）
It is important THAT you study. ← 你学这个事实很重要（事态）
两种都正确，但意味微妙不同。FCE 写作中灵活切换展示语言幅度。
It seems / It appears / It looks
| 词 | 用法 | 正式程度 |
|---|---|---|
| It seems | 最常用 | 中 |
| It appears | 更书面 | 高 |
| It looks | 视觉线索推断 | 低（口语） |
It seems (that) the meeting has been cancelled.
It appears (that) there has been a mistake.
It looks like it's going to rain.（looks like + 名词从句，非 that）
😂 Grammar Joke
It is What It Is
Philosophy Professor: “It is necessary to question everything.” Student: “Is it necessary to question that?” Professor: “It appears that it is.” Student: “Then it is possible that it is not necessary?” Professor: “It seems that it is possible that it is not impossible.” Student: “It is a pity that it takes this long to say nothing.” Professor: “It is worth noting that you have just constructed six grammatically perfect ‘It + be + adj’ sentences.”
这段对话里藏了六个 It 形式主语句型：It is necessary, It appears, It is possible, It seems, It is a pity, It takes, It is worth——展示了 it 形式主语有多”实用”。
🏛 语言文化光点
“It” 是英语最忙碌的词
It 在英语里有三种截然不同的用法：
- 指代代词：The cat stretched. It yawned.（指猫）
- 天气/时间/距离：It’s raining. It’s 5 o’clock. It’s far.
- 形式主语：It is important to sleep.
三种用法，同一个词。这体现了英语的经济原则：与其造新词，不如把现有词的用途扩大。
拉丁语和德语也有类似的形式主语（拉丁语的 id，德语的 es），这可能是印欧语系的共同倾向。重心后置（把最重要的信息留在句末）是人类语言的普遍规律——结尾的位置有天然的强调效果。所以英语用 it 来占位，把真正重要的内容推到句末，正是顺应了这个规律。
例题精讲
例1（📙 PET · 基础造句）
改写：To finish this project in one day is impossible.
答案：It is impossible to finish this project in one day.
例2（📙 PET · takes 句型）
用 “It takes” 翻译：“我从家里走到学校要 20 分钟。”
答案：It takes me 20 minutes to walk from home to school.
例3（📙 PET · seem + that）
填空：_____ seems _____ nobody was home when the parcel arrived.
答案：It seems that nobody was home when the parcel arrived.
例4（中考 · to do vs that）
选择：It is necessary _____ (A. to pass B. that pass C. that passing D. pass) the exam.
答案：A。It + be + adj + to do sth（不定式）。
例5（📕 FCE · 改写扩展）
改写：Clearly, she made the right decision. → It is _____.
答案：It is clear that she made the right decision. （It + be + adj + that 从句）
例6（中考 · no use）
填空：”_____ no use _____ (worry) about things you can’t change.”
答案：It is no use worrying. （It is no use + V-ing，动名词形式）
📖 Real English · 真实阅读
🔵 The Long Walk
It took Hillary and Tenzing 29 days to reach Base Camp. It was not easy to plan such an expedition in 1953 — there were no satellites, no GPS, and no reliable weather forecasts. It was essential to trust your partners completely. When they finally stood at the summit of Everest, it took a moment before either of them could speak. “It is impossible to describe,” Hillary said later. “It seemed that the whole world was below us.” It is worth remembering that they came down safely — which, as any climber knows, is the harder part.
🔵 Learning to Say Sorry
It is not always easy to apologise. It takes courage to admit you were wrong — especially when you believe, deep down, that you were right. It is possible to apologise without meaning it, of course. But it seems that a hollow apology often makes things worse. “It appears that people can tell when you don’t mean it,” said Dr. Santos, a psychologist who studies forgiveness. “It is fascinating that even young children can detect insincerity. It is a shame that adults often forget this.” She paused. “It takes practice. But it is worth it.”
🔵 The New Language
It took me three years before I could dream in English. At first, it seemed impossible that I would ever stop translating in my head. It is strange how the brain works — it is not clear exactly when the switch happens. One morning, it was simply there: I woke from a dream in which everything had been said in English without effort. It appears that language eventually stops being something you do and becomes something you are. It is difficult to explain this to someone who has not experienced it. It is a little like learning to ride a bicycle — at some point, it just works.
📝 中文注释（先读完英文再展开）
长途跋涉：It took + sb + 时间 + to do（花了29天到达）；It was not easy to plan（形式主语+不定式）；It was essential to trust（重要的是信任）；It is impossible to describe（不可能描述）；It seemed that（看似）；It is worth remembering（值得记住）。
学会道歉：连续多个 It is + adj + to do 展示句式多样性——not easy, takes courage, possible, seems, appears, fascinating, a shame, takes practice, worth it。注意 “It takes courage”（takes 不定式），“It is worth it”（it = the effort，这里 it 是指代词，不是形式主语）。
新语言：It took me + 时间 + before…（花了多久才…）；It seemed impossible that（看似不可能的是）；It is strange how（奇怪的是怎么）；It is not clear exactly when（不清楚确切是什么时候）；It appears that（看来）；It is difficult to explain（难以解释）；It is a little like…（有点像）。
练习题
📙 PET 基础（5题）
- _____ takes about 30 minutes to walk to the city centre.
- _____ is important _____ (drink) enough water every day.
- _____ seems _____ everyone enjoyed the concert.
- 改写：To speak in front of a crowd is terrifying. → _____
- 翻译：“这没有用——哭也没用。” → _____
中考 / 高考综合（3题）
- 用 It 形式主语改写： “That she passed the exam surprised everyone.” → _____
- 完成句子： “It took the builders three years _____ the bridge.”（完成这座桥）
- 改错：
“It is no use to argue with him.”（注意 no use 后接 V-ing）
🔗 节点关系
代词 Pronouns（it 的三种用法：指代 / 天气时间 / 形式主语）
↓
It 形式主语 ──┬── It + be + adj + to do ← 不定式与动名词
├── It + be + adj + that ← 宾语从句
├── It takes + 时间 + to do（时间表达）
└── It seems / appears / looks like（推断表达）
双链跳转： 代词 Pronouns | 动名词与不定式 Gerunds & Infinitives | 宾语从句 Object Clauses | 主谓一致 Subject-Verb Agreement