8. What is interchangeability?
Interchangeability means that any human being can be both a producer and a receiver of messages. Though some people suggest that there is sex differentiation in the actual language use, in other words, men and women may say different things, yet in principle there is no sound, or word or sentence that a man can utter and a woman cannot, or vice versa. On the other hand, a person can be the speaker while the other person is the listener and as the turn moves on to the listener, he can be the speaker and the first speaker is to listen. It is turn-taking that makes social communication possible and acceptable. Some male birds, however, utter some calls which females do not (or cannot). When a dog barks, all the neighboring dogs bark. Then people around can hardly tell which dog (dogs) is (are) “speaking” and which listening.

9.Why do linguists say language is human specific?
First of all, human language has six “design features” which animal communication systems do not have, at least not in the true sense of them. Secondly, linguists have done a lot trying to teach animals such as chimpanzees to speak a human language but have achieved nothing inspiring. Washoe, a female chimpanzee, was brought up like a human child by Beatnice and Alan Gardner. She was taught “American sign Language”, and learned a little that made the teachers happy but did mot make the linguistics circle happy, for few believed in teaching chimpanzees. Thirdly, a human child reared among animals cannot speak a human language, not even when he is taken back and taught to do so.

10. What functions does language have?
Language has at least seven functions: phatic, directive, Informative, interrogative, expressive, evocative and performative. According to Wang Gang (1988,p.11), language has three main functions: a tool of communication, a tool whereby people learn about the world, and a tool by which people learn about the world, and a tool by which people create art . M .A. K. Halliday, representative of the London school, recognizes three “Macro-Functions”: ideational, interpersonal and textual.

11. What is the phatic function?
The “phatic function” refers to language being used for setting up a certain atmosphere or maintaining social contacts(rather than for exchanging information or ideas). Greetings, farewells, and comments on the weather in English and on clothing in Chinese all serve this function. Much of the phatic language (e.g. “How are you?” “Fine, thanks.”) is insincere if taken literally, but it is important. If you don't say “Hello” to a friend you meet, or if you don’t answer his “Hi”, you ruin your friendship.

12. What is the directive function?
The “directive function” means that language may be used to get the hearer to do something. Most imperative sentences perform this function, e. g., “Tell me the result when you finish.” Other syntactic structures or sentences of other sorts can, according to J. Austin and J. Searle’s “Indirect speech act theory” at least, serve the purpose of direction too, e.g., “If I were you, I would have blushed to the bottom of my ears!”

13. What is the informative function?
Language serves an “informational function” when used to tell something, characterized by the use of declarative sentences. Informative statements are often labelled as true (truth) or false (falsehood). According to P. Grice’s “Cooperative Principle”, one ought not to violate the “Maxim of Quality”, when he is informing at all.

14. What is the interrogative function?
When language is used to obtain information, it serves an “interrogative function”. This includes all questions that expect replies, statements, imperatives etc., according to the “indirect speech act theory”, may have this function as well, e.g., “I’d like to know you better.” This may bring forth a lot of personal information. Note that rhetorical questions make an exception, since they demand no answer, at least not the reader’s/listener’s answer.

15. What is the expressive function?
The “expressive function” is the use of language to reveal something about the feelings or attitudes of the speaker. Subconscious emotional ejaculations are good examples, like “Good heavens!” “My God!” Sentences like “I’m sorry about the delay” can serve as good examples too, though in a subtle way. While language is used for the informative function to pass judgment on the truth or falsehood of statements, language used for the expressive function evaluates, appraises or asserts the speaker’s own attitudes.