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A rabbit is running into its hole. You may ask, “What happened?”
Well, when a rabbit sees something dangerous, it runs away. Its tail moves up and down as it runs. When other rabbits see this tail moving up and down, they run too. They know that there is danger. The rabbit has told them something without making a sound. It has given them a signal（信号）.
Many other animals use this kind of language. When a bee found some food, it goes back to his home. It cannot tell the other bees where the food is by speaking to them, but it does a little dance in the air. This tells the bees where the food is.
Some animals say things by making sounds. A dog barks, for example, when a stranger comes near. A cat purrs (发出呼噜呼噜的声音) when pleased. Some birds make several different sounds, each with its own meaning.
But human beings have something that no animals have -- a large number of words about things, actions, feelings or ideas. We are able to give each other information, to tell or inform other people what is in our mind or how we feel. By writing words down we can remind ourselves of the things what have happened, or send messages to people far away. No animals can do this. No animals has the wonderful power of language.
No one knows how man learned to make words. Somehow he learned to make them. As centuries went by, he made more and more new words. This is what we mean by language.
People living in different countries made different kinds of words. Today there are about fifteen hundred different languages in the world. A very large English dictionary, for example, contains four or five hundred thousand words. But we do not know all these. The words we know are called vocabulary. We should try to make our vocabulary larger. Read as many books as possible. When we meet a new word, look it up in the dictionary. A dictionary is the most useful book.