Green is an important color in nature. It is the color of grass and the leaves on trees. It is also the color of most growing plants. Sometimes, the word "green" means young, fresh and growing. For example, a greenborn is someone who has no experience. In the 15 th century, a greenborn was a young cow or an ox whose borns(角)had not yet developed. A century later, a greenborn was a soldier who had no experience in war. By the 18 th century, a greenborn had the meaning it has today—a person who is new in a job.

Someone who is good at growing plants is said to have a green thumb(大拇指). The expression comes from the early 20 th century. A person with a green thumb can make plants grow quickly and well. The Green Revolution(绿色革命)is the name given some years ago to the development of new kinds of rice and other grains. It was the result of hard work by agricultural scientists who had green thumbs.

Green is also the color used to describe the powerful feeling. Jealousy(嫉妒). The green eyed monster is not a dangerous animal from outer space. It is an expression used about 400 years ago by the British writer William Shakespeare in his play "Othello". It describes the unpleasant feeling when someone has something he wants.

In most places in the world, a green light is a signal(信号)to move ahead. In everyday speech, a green light means approval(赞成)to continue with a project.