You question is bit vague. I think you are asking what causes language disorder. Here are a few possibilities.
1. You can be born with some language disorders. The most obvious example is when you are born with hearing problems. This will hinder language acquisition.
2. You can undergo some sort of trauma and this may cause learning problems. One example of this is aphasia. This can happen if there is some damage to the language area of a person's brain.
3. There are also minor language problems, such as stuttering and the inability to pronounce certain words or even thing like a small lisp.
Some of the things mentioned above can be corrected, but others unfortunately cannot.
Aphasia, also called dysphasia is a fault generated by the brain in perceiving words. Symptoms of aphasia are associated with damage to brain tissues in a certain place and in a certain area.
A person affected by aphasia, although it is capable, for example, to move mouth partially, to pronounce certain sounds and understand spoken words, she/he is unable to form their own words. Another person affected by aphasia may be able to say a word but may be unable to say another word.
The main types of aphasia are:
- sensory form,
- motor form
- joint venture form (the result of sensory and motor association forms where one can dominate ).
All types of aphasia are important in psychology and psychiatry because it shows that the apparent unity of what is called normal mind remains in the interaction of independent functioning of parts of the brain, each of which can be destroyed without intervening in the functioning of other parts. Thus, it may seem that there is no such unity power as memory, visual memory being abolished without affecting the auditory device , olfactory, tactile, or any other memory functions.
Aphasia, pathological alterations of language is a handicap, consecutive to brain lesions located in the left hemisphere of right handed persons and can occur in subjects with normal intelligence and that does not present disturbances of affectivity and no deficiencies of perceptual and motor functions.
Aphasia is a loss of speech disturbances capacity to use the rules which produce and understand verbal messages. Aphasia is a disorder of the nervous system functions of the second signal and its interrelations with the first signaling system and characterized by memory loss of conventional signs of speech, of expression of these signs.
Person with Aphasia, in the absence of paralysis of phonation muscle can not express themselve in oral speech, to pronounce the words, though he has no auditory or optical disturbances, he can not understand the meaning of words