The three main categories of hearing loss are sensori-neural, conductive, and retrocochlear.
Sensori-neural hearing loss is permanent hearing loss typically resulting from damaged or missing hair cells in the cochlea, or from problems with the auditory nerves.
Conductive hearing loss is a permanent, intermittent, or temporary hearing loss resulting from problems in the parts of the hearing system that conduct sound to the cochlea, such as the ear drum or the bones in the middle ear.
Hearing loss can also be categorized based on the time it occurred: prelingual refers to a hearing loss that occurs before speech was established, postlingual refers to a hearing loss that occurs after speech developed.
Occasionally, sensorineural hearing loss is related to an actual problem with the hearing nerve or parts of the brain which process speech. These types of losses are called retrocochlear disorders.