Deafness overview

# Overview
The word deaf is used differently in different contexts, and there is some controversy over its meaning and implications.  In scientific and medical terms, deafness generally refers to a physical condition characterized by lack of sensitivity to sound.  Notated as deaf with a lowercase d, this refers to the audiological experience of someone who is partially or wholly lacking hearing.  In legal terms, deafness is defined by degree of hearing loss.  These degrees include profound or total deafness (90 dB - 120 dB or more of hearing loss), severe (60 dB - 90 dB), moderate (30 dB - 60 dB), and mild deafness (10 dB - 30 dB of hearing loss). Both severe and moderate deafness can be referred to as partial deafness or as hard of hearing, while mild deafness is usually called hard of hearing.
Within the Deaf community, the term "Deaf" is often capitalized when written, and it refers to a tight-knit cultural group of people whose primary language is signed, and who practice social and cultural norms which are distinct from those of the surrounding hearing community. This community does not automatically include all those who are clinically or legally deaf, nor does it exclude every hearing person. According to Baker and Padden, it includes any person or persons who "identifies him/herself as a member of the Deaf community, and other members accept that person as a part of the community."
Most deaf people, at least in developed countries, have some knowledge of the dominant language of their country. This may include the ability to lip read, to speak, or to read and write. Having some knowledge of both the dominant language and sign language is called bimodal bilingualism.

# Historical Perspective
Children of deaf adults (CODAs) with normal hearing ability may consider themselves, and be considered, culturally Deaf or as members of the deaf community.  In some cases they may need speech therapy due to limited exposure to spoken language.  An organization, also called CODA, was established in 1983 and now holds annual conferences.  There are also support groups for Deaf parents who may be concerned about raising their hearing children, as well as support groups for adult CODAs.
There are also several camps established for CODAs, such as the one at Camp Mark Seven which hosts two separate 2-week programs for CODAs, one from age 9 to 12 and one for CODAs from age 13 to 16 and it usually occurs during the summer, from the last week of June to mid-August.

# Epidemiology and Demographics
The global deaf population is roughly estimated to be 0.1% of the total population (1 in 1000). The figure is likely to be higher in developing countries than developed countries due to restricted access to health care, and, in some cultures, due to the high rate of intrafamilial marriages. The great majority of people with less than average hearing are elderly or developed hearing loss after leaving school.
According to the U.S. National Center for Health statistics, approximately three quarters of deaf and hard-of-hearing Americans experienced the onset of hearing loss after age 18.

# Identity and Culture
Within deaf culture, it is asserted that the label is one of identity, not audiological status. It is seen by them as akin to an ethnic division. It describes shared experiences in the world, not only those directly related to sight and sound (the increased awareness of one over the other) but also the cultural experiences that often inevitably follow from that. The term deaf then, used by many of those who are within the category, has little to do with an ability or inability to hear. Because of all this, and many other sociological forces, you will find some who identify themselves as deaf with much more ability to hear than many who self-identify as hearing or hard of hearing. In print, you can sometimes ascertain that the word is being used to reference the cultural identification because many people now capitalize the word when using it as a cultural label.
People who are part of Deaf culture typically use a sign language (such as American Sign Language) as their primary language and often emphatically see themselves as not disabled, but rather as members of a cultural or language minority. Members of this group use Deaf as a label of cultural identity much more than as an expression of hearing status. Hearing or hard of hearing people may also be considered culturally Deaf if they participate in Deaf culture and share Deaf cultural values; this is sometimes referred as 'attitudinal deafness'.