It is one of the branches of modern medicine which aims to treat speech defects, speech deterioration and the lack of language progression:

Delayed Language could be caused by reasons such as environmental deprivation, mental disability, auditory impairment, brain injury, autism or undetermined.

Speech Disorders include stuttering, nasality, dyslalia, pronunciation of the background letters in front ( K - C) T or D ) (Back to Front) and word obsession.

Sound Disorders include hoarseness and the loss of ability to release and perform high tones
Pronunciation problems include sound replacement, omission, distortion and additions