Education of students who are hard of hearing or deaf (see Deafness) may involve the use of powerful amplification devices, such as hearing aids, or it may use captions (printed words that appear on a television screen or computer monitor). Many deaf or hard of hearing students learn sign language, an organized system of gestures for communication. Others learn to speechread (lipread), a method of interpreting speech by "reading" the patterns of a person's mouth as he or she speaks. Some deaf students receive cochlear implants, which are receivers surgically implanted behind the ear and connected to electrodes placed in the cochlea of the inner ear, enabling individuals to hear sounds to a varying degree. See also Education of Deaf and Hard of Hearing Students.