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. Sometimes, it describes something that is not yet ripe or finished.
For example, a greenhorn is someone who has no expereince, who is new to a situation. In the 15th century, a greenhorn was a young cow or ox whose horns had not yet developed. A century or so later, a greenhorn was a soldier who had not yet had any experience in battle. By the 18th century, a greenhorn had the meaning it has today—a person who is new in a job.
Someone who has the ability to grow plants well is said to have a green thumb. The expression comes from the early 1900s. A person with a green thumb seems to have a magic touch that makes plants grow quickly and well. You might say that the woman next door has a green thumb if her garden continues to grow long after your plants have died.
The Green Revolution is the name given some years ago to the development of new kinds of rice and other grains. The new plants produced much larger crops. The Green Revolution was the result of hard work by agricultural scientists who had green thumbs.
Green is also the color used to describe the powerful emotion, jealousy. The green-eyed monster is not a frightening creature from outer space. It is an expression used about four hundred years ago by British writer William Shakespeare in his play Othello (《奥赛罗》). It describes the unplesant feeling a person has when someone has something he wants. A young man may suffer from the green-eyed monster if his girlfriend begins going out with someone else.
In most places in the world, a green light is a signal to move ahead. A green light on a traffic signal means your car can continue on. In everyday speech, a green light means approval to continue with a project.