it

1. PRON-SING You use it to refer to an object, animal, or other thing that has already been mentioned. 它 (指上文提及的某一物体、动物或其他事物)

It's a wonderful city, really. I'll show it to you if you want. 这确实是个很棒的城市。如果你愿意的话，我带你看一下。

My wife has become crippled by arthritis. She is embarrassed to ask the doctor about it. 我妻子因患关节炎腿瘸了。她不好意思去向医生询问相关病情。

2. PRON-SING You use it to refer to a child or baby whose sex you do not know or whose sex is not relevant to what you are saying. 它 (指小孩或婴儿)

She could compel him to support the child after it was born. 她可以迫使他在孩子出生后抚养孩子。

3. PRON-SING You use it to refer in a general way to a situation that you have just described. 它 (指刚刚说过的情况)

He was through with sports, not because he had to be but because he wanted it that way. 他放弃体育运动了，不是因为他非放弃不可，而是因为他想要那样。

4. PRON-SING You use it before certain nouns, adjectives, and verbs to introduce your feelings or point of view about a situation. 用于某些名词、形容词或动词前表达对某种情况的看法或观点

It was nice to see Steve again. 很高兴又见到了史蒂夫。

It's a pity you never got married, Sarah. 萨拉，很遗憾你从来没有结过婚。

5. PRON-SING You use it in passive clauses that report a situation or event. 用于被动句表示对某一情况或事件的报道

It has been said that stress causes cancer. 据说压力会诱发癌症。

6. PRON-SING You use it with some verbs that need a subject or object, although there is no noun that "it" refers to. 用作某些动词的形式主语或宾语

Of course, as it turned out, three-fourths of the people in the group were psychiatrists. 当然，结果证明这些人中3/4是精神病医生。

7. PRON-SING You use it as the subject of "be" to say what the time, day, or date is. 用作动词(be)的主语，指时间、日期等

It's three o'clock in the morning. 现在是凌晨3点。

It was a Monday, so she was at home. 那是个星期一，所以她在家。

8. PRON-SING You use it as the subject of a linking verb to describe the weather, the light, or the temperature. 用作系动词的主语，指天气、光、温度等

It was very wet and windy the day I drove over the hill to Del Norte. 我开车越过小山去德尔诺特的那天下大雨又刮大风。

9. PRON-SING You use it when you are telling someone who you are, or asking them who they are, especially at the beginning of a phone call. You also use it in statements and questions about the identity of other people. 通电话时用作开首语，报出身份或名字

"Who is it?" he called.—"It's your neighbour."

“谁呀？”他喊道。—“你的邻居。”

10. PRON When you are emphasizing or drawing attention to something, you can put that thing immediately after it and a form of the verb "be." 与(be)动词配合起强调作用，引起对某事物的注意[强调]

It's really the poor countries that don't have an economic base that have the worst environmental records. 确实是那些没有经济基础的贫穷国家的环保记录最糟糕。

11. PHRASE You use it in expressions such as it's not that or it's not just that when you are giving a reason for something and are suggesting that there are several other reasons. 用于(it's not that)、(it's not just that)等表达法中，表示提出一个理由并同时暗示还有其它一些理由

It's not that I didn't want to be with my family. 并不是因为我不愿意和我的家人在一起。

12. if it wasn't for→see be

13. the INTERNET DOMAIN NAME for Italy 意大利