We have five senses: sight, hearing, smell, taste and touch. Your eyes and brain work together so you can see. But not all people are able to see.
Blindness is the loss of sight. A person may be blind in one eye or in both eyes. Some people who are blind do not see at all. Others can see light and shadow. Some people become blind as a result of injury, while others may be born blind. Eye diseases, such as glaucoma, can also cause blindness. Although coping with a loss of sight can be challenging, blind people can live happy, active lives. For example, the blind can learn to travel safely from place to place with the help of teachers called mobility instructors.
Blind people can even learn to read thanks to a special system of raised dots called Braille. The dots stand for letters that can be "read" when they are felt with the fingers. The blind can also read with the help of technological advances like computer software that can change words into speech!