[简答题]

You probably have noticed that people express similar ideas in different ways, depending on the situations they are in. This is very natural. All languages have two general levels of usage—a formal level and an informal level. English is no exception. The difference in these two levels is the situation in which you use a particular level. Formal language is the kind of language you find in textbooks, reference books and in business letters. You would also use formal English in compositions and essays that you write in school. Informal language is used in conversation with colleagues, family members and friends, and when we write personal notes or letters to close friends.
Formal language is different from informal language in several ways. First, formal language tends to be more polite. What we may find interesting is that it usually takes more words to be polite. For example, I might say to a friend or a family member "Close the door, please." But to a st