What is Aphonia?

Legal Definition
Aphonia is defined as the inability to produce voiced sound. A primary cause of aphonia is bilateral disruption of the recurrent laryngeal nerve, which supplies nearly all the muscles in the larynx. Damage to the nerve may be the result of surgery (e.g., thyroidectomy) or a tumor.

Aphonia means "no sound." In other words, a person with this disorder has lost his/her voice.
-- Wikipedia
Legal Definition
In medical jurisprudence. Loss of the power of articulate speech in consequence of morbid conditions of some of the vocal organs. It may be incomplete, in which case the patient can whisper. It is to be distinguished from congenital dumbness, and from temporary loss of voice through extreme hoarseness or minor affections of the vocal cords, as also from aphasia, the latter being a disease of the brain without impairment of the organs of speech.
-- Black's Law Dictionary