2. Passage Seventeen No one knows how man learned to make words. Perhaps he began by making sounds like those made by animals. Perhaps he grunted like a pig when he lifted something heavy. Perhaps he made sounds like those he heard all round him——water splashing， bees humming， a stone falling to the ground. Somehow， he learned to make words. As the 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. Each contains many thousands of words. A very large English dictionary， for example， contains four or five hundred thousand words. But we do not need all these. Only a few thousand words are used in everyday life. The words you know are called your vocabulary. You should try to make your vocabulary bigger. You’re supposed to read as many books as you can. There are plenty of books written in easy English for you to read. You will enjoy them. When you meet a new word， you should find it in your dictionary. Your dictionary is your most useful book.The number of different languages spoken is about ( ) .