The most common disease in the world is the cold. It often starts with a sore throat(噪子痛).You sneeze and your nose runs. You usually have a headache too. Often you have a cough. It's not a serious disease, but you can feel quite ill.
There isn't a cure（特效药）for a cold, but you can take medicine（药）to make you feel better. It is good to rest, and to drink a lot of water, too. A doctor once told me "With the right medicine, a cold will last for seven days. With no medicine, it will still go on for a whole week!"
Where does our medicine come from? A long time ago, people understood that some plants made them feel better. They ate certain parts of plants, like the leaves, the fruit, or the seeds（籽）.For example, the juice of lemons makes a sore throat feel better.
In modern times, scientists have studied these plants, and found out what chemicals（化学物质）are in them. Much of our medicine today is made from those chemicals.
There are some diseases which we can't cure（治愈）yet. And nobody has found a cure for old age. But because of modern medicine, most of the people live longer than their grandparents.
