Autism is a developmental disability significantly affecting verbal and nonverbal communication and social interaction, generally evident before age three, that adversely affects a child's educational performance. (A child who manifests the characteristics of autism after age 3 could be diagnosed as having autism if the other criteria of this Section are satisfied.) Other characteristics often associated with autism are engagement in repetitive activities and stereotyped movements, resistance to environmental change or change in daily routines, and unusual responses to sensory experiences. The term does not apply if a child's educational performance is adversely affected primarily because the child has an emotional disturbance

Intellectual Disability means significantly subaverage general intellectual functioning, existing concurrently with deficits in adaptive behavior and manifested during the developmental period, that adversely affects a child's educational performance

Deaf-Blindness means concomitant hearing and visual impairments, the combination of which causes such severe communication and other developmental and educational needs that they cannot be accommodated in special education programs solely for children with deafness or children with blindness.

Deafness means a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification, that adversely affects a child's educational performance.

Developmental Delay means a delay in physical development, cognitive development, communication development, social or emotional development, or adaptive development (may include children from three through nine years of age.)

Emotional Disability (includes schizophrenia but does not apply to children who are socially maladjusted, unless it is determined that they have an emotional disturbance) means 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: 
1) An inability to learn that cannot be explained by intellectual, sensory, or health factors;
2) An inability to build or maintain satisfactory interpersonal relationships with peers and teachers;
3) Inappropriate types of behavior or feelings under normal circumstances;
4) A general pervasive mood of anxiety or unhappiness or depression; or
5) A tendency to develop physical symptoms or fears associated with personal or school problems.

Hearing Impairments means an impairment in hearing, whether permanent or fluctuating, that adversely affects a child's educational performance but that is not included under the definition of deafness.

Multiple Disabilities means concomitant impairments (such as intellectual disability-blindness, intellectual disability-orthopedic impairment, etc.), the combination of which causes such severe educational needs that they cannot be accommodated in special education programs solely for one of the impairments. The term does not include deaf-blindness.

Orthopedic Impairment means a severe orthopedic impairment that adversely affects a child's educational performance. The term includes impairments caused by congenital anomaly (e.g., clubfoot, absence of some member, etc.), impairments caused by disease (e.g., Poliomyelitis, bone tuberculosis, etc.), and impairments from other causes ( e.g., cerebral palsy, amputations, and fractures or burns that cause contractures).

Other Health Impairment means having limited strength, vitality or alertness, including a heightened sensitivity to environmental stimuli, that results in limited alertness with respect to the educational environment that 1) is due to chronic or acute health problems such as asthma, attention deficit disorder or attention deficit hyperactivity disorder, diabetes, epilepsy, a heart condition, hemophilia, lead poisoning, leukemia, nephritis, rheumatic fever, or sickle cell anemia; and 2) adversely affects a child's educational performance.

Specific Learning Disabilities means a disorder in one or more of the basic psychological processes involved in understanding or in using language, spoken or written, that may manifest itself in an imperfect ability to listen, think, speak, read, write, spell, or do mathematical calculations, including such conditions as perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, and developmental aphasia. The term does not include learning problems that are primarily the result of visual, hearing or motor disabilities, of mental retardation, of emotional disturbance, or of environmental, cultural, or economic disadvantage. 

In accordance with 23 Illinois Administrative Code 226.130, beginning with the 2010-2011 school year, Illinois districts are required to use a process that determines how a child responds to scientific, research-based interventions as part of the evaluation procedures to determine special education eligibility under the category of specific learning disability (SLD).  While this requirement is specific to SLD, districts also have the option of using such a process as part of the evaluation procedures for other disability categories.

Speech or Language Impairment means a communication disorder, such as stuttering, impaired articulation, a language impairment, or a voice impairment, that adversely affects a child's educational performance.

Traumatic Brain Injury means an acquired injury to the brain caused by an external physical force, resulting in total or partial functional disability or psychosocial impairment, or both, that adversely affects a child's educational performance. The term applies to open or closed head injuries resulting in impairments in one or more areas, such as cognition; language; memory; attention; reasoning; abstract thinking; judgment; problem-solving; sensory, perceptual, and motor abilities; psychosocial behavior; psychosocial functions; information processing; and speech. The term does not apply to brain injuries that are congenital or degenerative or to brain injuries induced by birth trauma.

Visual Impairment means an impairment in vision that, even with correction, adversely affects a child's educational performance. The term includes both partial sight and blindness.