Deaf means unable to hear, or having very limited hearing. Some people are born deaf, while others lose their hearing later in life from illness, injury, or age. A person who is deaf might not hear a fire alarm, a whispered secret, or music playing in another room.

Many deaf people communicate using sign language, a complete language expressed through hand shapes, movements, and facial expressions rather than spoken words. American Sign Language (ASL) has its own grammar and vocabulary, just like English or Spanish. Deaf communities around the world have rich cultures and histories built around visual communication.

The word can also describe situations where hearing is blocked or impaired: loud construction noise might leave you temporarily unable to hear normal conversation, or saying “turn a deaf ear” means deliberately ignoring something you don't want to hear.

Some people use “Deaf” with a capital D to refer specifically to people who identify with Deaf culture and community, while “deaf” with a lowercase d simply describes the medical condition of not hearing. Modern technology like hearing aids and cochlear implants can help some deaf people hear, though many deaf people live full, successful lives without them, using sign language and visual communication instead.