Science Fair Project Encyclopedia
The word deaf, can have very different meanings based on the background of the person speaking or the context in which the word is used. The term is commonly used to mean having profound hearing impairment, a physiological condition causing an inability to receive or process aural stimulation.
Depending on the definition of deafness used, the global deaf population is estimated to be roughly 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. Worldwide, at least 5% (1 in 20) are estimated to have a hearing problem great enough to cause them some difficulty. The great majority of people with hearing impairments are elderly or acquired hearing loss after leaving school. 
A significant minority of deaf people are part of Deaf culture. They are mostly either individuals who were born deaf or became deaf at an early age, and who have a "severe or profound hearing loss"; they can also be children of deaf parents. They use sign 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. When the word is used in this way, it is often capitalized.
Deaf vs. Hearing Impaired
Outside of the deaf community deaf usually means a total hearing loss and someone with a partial hearing loss is more likely to be referred to as hearing impaired. These terms are used in the pathological sense, to indicate an illness or disability.
In contrast, the Deaf cultural worldview uses the terms deaf, hard-of-hearing and hearing in an "us" or "them" sense. In this view "deaf" (us) means to experience the world and embrace the values that deaf people embrace, while "hearing" (them) means to experience the world and embrace the values that hearing people embrace. This creates a deaf cultural view in which hard-of-hearing represents a view of the world that embraces values from both the deaf and hearing world. Indeed, within deaf culture the terms "hearing" and "hard-of-hearing" are sometimes used to denigrate, provoke or insult both deaf and hearing people. Deaf students from one school have been known to playfully refer to deaf students from another school as "hearing" during athletic competition. Historically speaking, deaf culture has never embraced the term "hearing impaired" in this "us" versus "them" view because it is thought to be a generalization on pathology that tells nothing about an individual's values. Further, the deaf view of this terminology parallels that of a language minority rather than being a description of pathology or disability. The term "deaf" has been the traditional identification of culturally deaf people for over two and a half centuries, or before the serious examination of hearing loss by medical practitioners and speech teachers, who introduced pathological terminology such as "semi-deaf", "semi-mute" and the modern "hearing impaired" to the language, even began. "Deaf" remains the preferred term of group identification among culturally deaf people today.
Other meanings of 'deaf'
- Deaf is also used as a colloquialism to refer to a recalcitrant individual or someone unwilling to listen, obey or acknowledge an authority or partner. The third line of Shakespear's Sonnet 29 provides an example.
"When in disgrace with fortune and men's eyes
I all alone beweep my outcast state,
And trouble deaf heaven with my bootless cries,"
As an acronym
- The acronym DEAF is also used to refer to the Deaf Equipment Acquisition Fund.
Categories of deafness and hearing impairment
These categories may be overlapping. Deafness or hearing impairment may be:
- Limited (to tone)
- Models of deafness for a comparison of the medical, disability and cultural models of deafness.
- Deaf history
- Deaf education
- Late deafened adult
- List of deaf people
- Sign language
- National Deaf Children's Society
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