The two main types of hearing loss are sensori-neural (nerve deafness which involves impairment of the auditory nerve) and conductive deafness (usually a dysfunction of a part of the ear mechanism). Hearing loss is measured by decibels, and according to the decibel count the loss may be mild, moderate or profound.
More individuals in the United States have a hearing impairment than any other physical disability. The 21 million people in the United States who have this disability differ considerably. A person may be born with a hearing loss or may become hard of hearing because of an accident or illness.
If the age of onset occurs before the acquisition of language and the development of speech, the individual may have language-based deficiencies such as poor syntax and vocabulary, and difficulty understanding abstract concepts.