The National Association of the Deaf explains a distinction that shapes this whole course. Written with a lowercase d, deaf describes the audiological condition of not hearing. Written with a capital D, Deaf refers to people who share a language, American Sign Language, and a culture that has been created and passed down across generations. Deaf culture has its own history, arts, humor, values, social norms and institutions. Many Deaf people see themselves first as members of a linguistic minority, not as people defined by a hearing loss.
The National Institute on Deafness and Other Communication Disorders describes ASL as a complete, natural language with the same linguistic properties as spoken languages and a grammar that differs from English. ASL uses the hands, face and body, and has its own rules for pronunciation, word formation and word order. It has regional accents and dialects. It is not universal: British Sign Language, for example, is a different language, and signers of one cannot necessarily understand the other. ASL grew over two centuries from a mix of local sign languages and French Sign Language. Fingerspelling is used for names and some English words, but it is a small part of the language.
This has a practical consequence that is easy to miss. For many Deaf people, ASL is their first or strongest language and English is a second language. Handing someone a written notice, or offering to pass notes, may not be effective communication for a person whose primary language is ASL, especially for complex topics like eligibility, services or rights. The reverse is also true: some deaf people do not know ASL and rely on written English, captioning or speech reading.
Language about deafness matters. The NAD notes that most people in the community reject the term hearing impaired because it focuses on what people cannot do, and considers terms like deaf and dumb or deaf-mute offensive. Deaf, DeafBlind and hard of hearing are widely accepted. The NAD's core advice is simple: when in doubt, ask the person how they identify.