【形式主语it的用法】在英语语法中，"it" 作为形式主语是一种常见的语言现象。它通常用于句子中，代替真正的主语，使句子结构更加平衡或符合习惯表达方式。形式主语 "it" 并不具有实际意义，而是起到引导作用，真正主语则常常是动词不定式、从句或动名词等。
以下是对“形式主语it的用法”的总结与归纳：
一、形式主语it的基本用法
| 类型 | 例子 | 说明 |
| It + be + 形容词 + that从句 | It is important that he arrives on time. | “it”作为形式主语，真正的主语是后面的that从句。 |
| It + be + 名词 + that从句 | It is a pity that she couldn’t come. | “it”作形式主语，真正的主语是后面的that从句。 |
| It + 动词 + to do something | It is hard to understand him. | “it”作形式主语，真正的主语是动词不定式短语。 |
| It + be + doing something | It is no use crying over spilled milk. | “it”作形式主语，真正的主语是动名词短语。 |
| It + seem/appear/happen/look + that从句 | It seems that he is not coming. | “it”作为形式主语，真正的主语是that从句。 |
二、形式主语it的常见结构
| 结构 | 例句 | 说明 |
| It is + adj. + that从句 | It is clear that he is lying. | “it”是形式主语，that从句是真正主语。 |
| It is + n. + that从句 | It is a fact that the earth is round. | “it”是形式主语，that从句是真正主语。 |
| It is + to do sth | It is easy to learn English. | “it”是形式主语，to do是真正主语。 |
| It is + doing sth | It is fun playing football. | “it”是形式主语，doing是真正主语。 |
| It + be + 过去分词 + that从句 | It is said that he will resign. | “it”是形式主语，that从句是真正主语。 |
三、形式主语it的使用目的
1. 保持句子平衡：当句子的主语较长时，使用形式主语可以避免头重脚轻。
2. 使语言更自然：某些表达习惯上必须使用形式主语，如“It is said that...”。
3. 突出谓语动词：通过形式主语，可以更突出句子的谓语部分，增强表达效果。
四、注意事项
- 形式主语 "it" 不可随意省略，否则句子结构可能不完整。
- 在使用形式主语时，需注意其后接的从句或短语是否正确。
- 形式主语常用于正式或书面语中，口语中有时会省略。
五、总结
形式主语 "it" 是英语中一种重要的语法现象，广泛用于各种句型结构中。它不仅有助于句子结构的平衡，还能使表达更加自然和地道。掌握其用法，有助于提高英语写作和口语表达的准确性与流畅性。
（表格总结版）
| 用法类型 | 例句 | 说明 |
| it + be + adj. + that从句 | It is necessary that we leave now. | 形式主语+形容词+that从句 |
| it + be + noun + that从句 | It is a surprise that she passed the exam. | 形式主语+名词+that从句 |
| it + be + to do | It is difficult to answer this question. | 形式主语+不定式 |
| it + be + doing | It is interesting learning new languages. | 形式主语+动名词 |
| it + seem/appear + that从句 | It seems that he is tired. | 形式主语+情态动词+that从句 |
以上内容为原创整理，结合了语法理论与实际应用，旨在帮助学习者更好地理解和掌握形式主语 "it" 的用法。
