作者：石海棠
　　【Abstract】“It”，it is the third person singular of personal pronoun in English.In grammar， it is used as the subject or the object of a sentence.And it is usually used to replace concrete lifeless things and animals except human beings.In fact，“it”can be also used to refer to something abstract such as time， distance， nature states， surroundings.Sometimes“it” can be also used to refer to human beings . In addition， “It” can be used to take the place of the subjects or objects which are made of some phrases or clauses. In the cases，“it” ， in grammar， is called the formal subject or formal object .
　　【Key words】it; replace; refer to; concrete lifeless things; something abstract; grammartical functions
　　【作者簡介】石海棠，，湖北省黄石市第十六中学。
　　“It”，it is the third person singular of personal pronoun in English.In grammar， it is used as the subject or the object of a sentence.And it is usually used to replace all concrete lifeless things and animals except human beings. In Chinese “it” means “它”.
　　e. g. （1）What’s this？ It is a book.
　　（2） Where’s my cat？ It is under the bed.
　　In fact，“it”can be also used to refer to something abstract. The situation mainly has the following some types：
　　1. Referring to time.
　　e.g. （1） What time is it？ It’s six o’clock.
　　（2）It’s September， and we’re back at school.
　　2. Referring to distance.
　　e.g. （1）It’s not far from hereto the bus stop.
　　（2） It’s about five minutes’ walk from my home to the school.
　　3. Referring to nature states.
　　e.g. （1） It’s cold today， isn’t it？
　　（2） I hope it will be fine tomorrow.
　　4. Referring to surroundings.
　　e.g. （1） Itwas very quiet at the moment.
　　（2） It is quite close （rather stuffy） in the room. Let’s open the window for a while.
　　Sometimes“it” can be also used to refer to human beings . This kind of usage is often used in the following situations.
　　1. When the sex isn’t known or the sex isn’t important， the pronoun “it” can be used for referring to infants.
　　e.g. （1） Who’s the child？ It is Tom’s little sister.
　　（2） I have seen her baby. It’s very active and lovely.
　　2. The pronoun “it” can be used for referring to the person in our mind or the person who has been told in the last contents or will be told in the next contents.
　　i.e， “it” can be used in referring to the person when we telephone or when somebody is knocking at the door（ or the window）.