A language is a signaling system which operates with symbolic vocal sounds (语声), and which is used by a group of people for the purpose of communication.
Let’’s look at this (61)______ in more detail because it is language, more than anything else, (62)______ distinguishes man from the rest of the (63)______ world.
Other animals, it is true, communicate with one another by (64)______ of cries: for example, many birds utter (65)______ calls at the approach of danger; monkeys utter (66)______ cries, such as expressions of anger, fear and pleasure. (67)______ these various means of communication differ in important ways (68)______ human language. For instance, animals’’ cries do not (69)______ thoughts and feelings clearly. This means, basically, that they lack structure. They lack the kind of structure that (70)______ us to divide a human utterance into (71)______
We can change an utterance by (72)______ one word in it with (73)______ : a good illustration of this is a soldier who can say, e.g. , "tanks approaching from the north", (74)______ who can change one word and say "aircraft approaching from the north" or "tanks approaching from the west"; but a bird has a single alarm cry, (75)______ means "danger!"
This is why the number of (76)______ that an animal can make is very limited: the great tit (山雀) is a case (77)______ point; it has about twenty different calls, (78)______ in human language the number of possible utterances is (79)______ . It also explains why animal cries are very (80)______ in meaning.