Muteness

Muteness or mutism (from Latin mutus, meaning 'silent') is an inability to speak often caused by a speech disorder, hearing loss, or surgery. Someone who is mute may be so due to the unwillingness to speak in certain social situations.

Those who are physically mute may have problems with the parts of the human body required for human speech (the esophagus, vocal cords, lungs, mouth, or tongue, etc.).

Trauma or injury to Broca's area, located in the left inferior frontal cortex of the brain, can cause muteness.

Selective mutism previously known as "elective mutism" is an anxiety disorder very common among young children, characterized by the inability to speak in certain situations. It should not to be confused with someone who is mute and cannot communicate due to physical disabilities. Selectively mute children are able to communicate in situations in which they feel comfortable. About 90% of children with this disorder have also been diagnosed with social anxiety. It is very common for symptoms to occur before the age of five and do not have a set time period. Not all children express the same symptoms. Some may stand motionless and freeze in specific social settings and have no communication whatsoever.

Alalia is a disorder that refers to a delay in the development of speaking abilities in children. In severe cases, some children never learn how to speak. It is caused by illness of the child or the parents, the general disorders of the muscles, the shyness of the child or that the parents are close relatives.

Anarthria is a severe form of dysarthria. The coordination of movements of the mouth and tongue or the conscious coordination of the lungs are damaged.

Aphasia can rob all aspects of the speech and language. It is a damage of the cerebral centres of the language.

Aphonia is the inability to produce any voice. In severe cases the patient loses phonation. It is caused by the injury, paralysis, and illness of the vocal box.

...
Wikipedia