When we want to tell other people what we think, we can do it not only with the help of words, but also in many other ways. Words consist of sounds, but there are many sounds which have a meaning and yet are not words. For example, we may say "Sh-sh-sh" when we mean "keep silent." When babies laugh, we know they are happy, and when they cry, we know they are ill or simply want something. It is the same with animals. When a dog says "G-r-r" or a cat says "F-f-f" we know they are angry. But these sounds are not language. Language consists of words which we put together into sentences. But animals can not do this: a dog can say "G-r-r" when he means "I am angry," but he cannot say first "I" and then "am" and they "angry." A parrot can talk like a man; it can repeat whole sentences and knows what they mean. We may say that a parrot talks, but cannot say that it really speaks, because it cannot from new sentences out of the words it knows. Only man has the power to do this.