Disability Definitions


Autism (aka Autistic spectrum disorder) and other Pervasive Developmental Disorders are neurological disorders that affect a child’s ability to communicate, understand language, play, and relate to others. 

Blindness and Visual Impairment 

The terms partially sighted, low vision, legally blind, and totally blind are used in the educational context to describe students with visual impairments. They are defined as follows: 

"Partially sighted" indicates some type of visual problem has resulted in a need for special education;

"Low vision" generally refers to a severe visual impairment, not necessarily limited to distance vision. Low vision applies to all individuals with sight who are unable to read the newspaper at a normal viewing distance, even with the aid of eyeglasses or contact lenses. They use a combination of vision and other senses to learn, although they may require adaptations in lighting or the size of print, and, sometimes, braille;

"Legally blind" indicates that a person has less than 20/200 vision in the better eye or a very limited field of vision (20 degrees at its widest point); and 

Totally blind students learn via braille or other non-visual media.

Deafness and Hearing Impairment 

Deafness is defined [by the Individuals with Disabilities Education Act (IDEA)] as "a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification." 

Hearing impairment is defined by IDEA as "an impairment in hearing, whether permanent or fluctuating, that adversely affects a child's educational performance."

Thus, deafness may be viewed as a condition that prevents an individual from receiving sound in all or most of its forms. In contrast, a child with a hearing loss can generally respond to auditory stimuli, including speech. 

Emotional Disturbance  

Emotional disturbance ... is defined [by the Individuals with Disabilities Education Act (IDEA)] as "a condition exhibiting one or more of the following characteristics over a long period of time and to a marked degree that adversely affects a child's educational performance --

  • an inability to learn that cannot be explained by intellectual, sensory, or health factors;
  • an inability to build or maintain satisfactory interpersonal relationships with peers and teachers;
  • inappropriate types of behavior or feelings under normal circumstances;
  • a general pervasive mood of unhappiness or depression; and
  • a tendency to develop physical symptoms or fears associated with personal or school problems." 

Students with emotional and/or behavioral disabilities may exhibit:

  • hyperactivity (short attention span, impulsiveness);
  • aggression/self-injurious behavior (acting out, fighting);
  • withdrawal (failure to initiate interaction with others, retreat from exchanges of social interaction, excessive fear or anxiety);
  • immaturity (inappropriate crying, temper tantrums, poor coping skills); and
  • learning difficulties (academically performing below grade level).  


Multiple Disabilities 

People with severe disabilities are those who traditionally have been labeled as having severe to profound mental retardation. These people require ongoing, extensive support in more than one major life activity in order to participate in integrated community settings and enjoy the quality of life available to people with fewer or no disabilities. They frequently have additional disabilities, including movement difficulties, sensory losses, and behavior problems.

Speech and Language Impairment 

Speech and language disorders refer to problems in communication and related areas such as oral motor function. These delays and disorders range from simple sound substitutions to the inability to understand or use language or use the oral-motor mechanism for functional speech and feeding. Some causes of speech and language disorders include hearing loss, neurological disorders, brain injury, mental retardation, drug abuse, physical impairments such as cleft lip or palate, and vocal abuse or misuse. 

It is estimated that communication disorders (including speech, language, and hearing disorders) affect one of every 10 people in the United States.

NICHCY Speech and Language Impairments Fact Sheet

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