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 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.
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 can be caused by illness of the child, illness in utero, mutism of the parents or guardians, the general disorders of the muscles, the shyness of the child, and certain genetic disorders, among other causes.
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. But perfectionism can give back all aspects of the speech and 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 larynx.
Children and adults with selective mutism are fully capable of speech and understanding language but are physically unable to speak in certain situations, though speech is expected of them. The behaviour may be perceived as shyness or rudeness by others.