Hearing Threshold: The weakest sounds that a person can detect for any particular frequency.

Hereditary Hearing Impairment - hearing loss passed down through generations of a family.

Inner Ear - part of the ear that contains both the organ of hearing (the cochlea) and the organ of balance (the labyrinth).

In The Canal Hearing Aids - ITC hearing aids are tiny devices that fit into the ear canal, with only a part of the instrument showing. The microphone, circuitry and amplifier are all contained in the single device. Generally not for people with severe hearing loss, or for children (for whom it is often difficult to fit).

In The Ear Hearing Aids - ITE hearing aids are slightly larger than the Completely In The Canal and In the Canal models, with more of the device visible. The microphone, circuitry and amplifier are all contained in the single device.

Labyrinth - organ of balance located in the inner ear. The labyrinth consists of three semicircular canals and the vestibule.

Labyrinthine Hydrops - excessive fluid in the organ of balance (labyrinth); can cause pressure or fullness in the ears, hearing loss, dizziness, and loss of balance.
Labyrinthitis - viral or bacterial infection or inflammation of the inner ear that can cause dizziness, loss of balance, and temporary hearing loss.

Landau-Kleffner Syndrome - childhood disorder of unknown origin which often extends into adulthood and can be identified by gradual or sudden loss of the ability to understand and use spoken language.

Lip Reading - Also called Speech Reading. Lip reading involves watching a speaker's lips and facial expressions to derive more meaning from their speech.  With proper lip or speech reading training, comprehension levels can soar. With sound alone, my comprehension levels are sub 50 percent. With lip reading, I can comprehend 90 percent or more of the spoken word. Everyone does it to some extent.

Meningitis - inflammation of the meninges, the membranes that envelop the brain and the spinal cord; may cause hearing loss or deafness.

Microphone - the part of a hearing aid that collects sound and sends it to the signal processor.

Middle Ear - part of the ear that includes the eardrum and three tiny bones of the middle ear, ending at the round window that leads to the inner ear. It contains the ossicles that transmit vibrations from the eardrum to the inner ear's fluid. This causes a wave in the fluid, which is sent via the auditory nerve to the brain.