Definition for Deafness
From Biology Forums Dictionary
1) When a person's ability to perceive sound is limited to such an extent that the auditory channel is not the primary sensory input for communication. It may be congenital or acquired.
2) Hearing loss, usually caused by damage to the hair cells within the cochlea, although some cases result from functional problems in brain areas that process sound or in nerves that carry information to the brain from the hair cells.