Language and Communication 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(51)in more detail because it is language, more than anything else,(52)distinguishes man from the rest of the physical world. Other animals, it is true, communicate with one another by(53)of cries: for example, many birds utter(54)calls at the approach of danger; monkeys utter(55)cries, such as expressions of anger, fear and pleasure.(56)these various means of communication differ in important ways from human language. For instance, animals' cries do not(57)thoughts and feelings clearly. This means, basically, that they lack structure. They lack the kind of structure that(58)us to divide a human utterance into(59). We can change an utterance by replacing one word in it with(60): a good illustration of this is a soldier who can say, e.g., 'tanks approaching from the north',(61)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,(62)means 'danger!' This is why the number of signals that an animal can make is very limited: the great tit (山雀) is a case(63)point; it has about twenty different calls,(64)in human language the number of possible utterances is limitless. It also explains why animal cries are very(65)in meaning.