In public places, people often use body language to express their meanings. Waving and bowing are examples of body language. Different kinds of body languages show different cultures in different countries. In China waving means greeting, but in Japan bowing is used. Sometimes this kind of body language is polite in one country, but it is not polite in another. We should pay attention to using it. In China, nodding your head shows you agree with someone, but in India, shaking your head from side to side shows agreement. In China, people hold hands as a sign of friendship, but people seldom hold hands in North America. It is worth (值得) noting that different meanings of body language can also cause problems in understanding. Some people do not understand how to use thumb (拇指) correctly. Most people often show one thumb to praise someone or something. You can't raise your thumb when someone is in danger. In a basketball match, if the judge shows two thumbs, it means two players break the rules.
