The Deaf, the deafened, and the hard of hearing are all very distinct groups. Using the proper terminology shows respect for their differences.
A medical/audiological term referring to those people who have little or no functional hearing. May also be used as a collective noun ("the deaf") to refer to people who are medically deaf but who do not necessarily identify with the Deaf community.
Deaf (with capital D):
A sociological term referring to those individuals who are medically deaf or hard of hearing who identify with and participate in the culture, society, and language of Deaf people, which is based on Sign language. Their preferred mode of communication is Sign.
deafened (Also known as late-deafened):
This is both a medical and a sociological term referring to individuals who have become deaf later in life and who may not be able to identify with either the Deaf or the hard of hearing communities.
hard of hearing:
A person whose hearing loss ranges from mild to profound and whose usual means of communication is speech. It is both a medical and a sociological term.
This term is not acceptable in referring to people with a hearing loss. It should never be used in referring to Deaf people. "Hearing impaired" is a medical condition; it is not a collective noun for people who have varying degrees of hearing loss. It fails to recognize the differences between the Deaf and the hard of hearing communities.
A deaf person whose preferred mode of communication is verbal and auditory and/or lipreading. An oral deaf person who can both Sign and speak can be considered "Deaf" if he/she is accepted as such by other Deaf persons and uses Sign within the Deaf community.
Unacceptable. A deaf person may choose not to use his/her voice; this does not make him/her a "mute".
deaf and dumb
The Greek philosopher, Aristotle, pronounced us "deaf and dumb", because he felt that deaf people were incapable of being taught, of learning, and of reasoned thinking. It is an archaic term that is considered offensive.