Glossary Terms: D

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Deaf (deafness, hearing loss)
The partial or extreme loss of or inability for a person to receive information through hearing/ listening without the assistance of hearing technology. Any degree of deafness, from mild to profound, has the potential to impact a child’s language, communication and academic development without proper intervention.

Deaf-Blind
Educationally significant loss of vision and hearing.

Decibel
Unit that measures the intensity or loudness of sound.

Designated Instruction Services (DIS)
Instruction and services not normally provided by regular classes, resource specialist programs or special day classes. They include speech therapy and adaptive physical education.

Developmental Delay
A disability category that states may use for certain students aged 3 through 9 years as a way to provide early services for students suspected of having a disability. If used, the definition of developmental delay is determined by the state and may include a child whose development, as measured by appropriate diagnostic tests and procedures, lags behind peers in one or more of the following areas: physical development, cognitive development, communication development, social or emotional development or adaptive development and who, because of such delays, needs special education and related services.

Differential Standards for Graduation
Standards for graduation that may be modified for students with exceptional needs.

Disability
Physical or mental impairment that substantially limits one or more major life activities.

Disability Categories
IDEA disability categories include autism, deaf-blindness, deafness, emotional disturbance, hearing impairment, mental retardation, multiple disabilities, orthopedic impairment, other health impairment (e.g., asthma, attention deficit disorder or attention deficit hyperactivity disorder, diabetes, epilepsy, heart condition, hemophilia, lead poisoning, leukemia, nephritis, rheumatic fever, sickle cell anemia and Tourette syndrome), specific learning disability, (e.g. perceptual disabilities, brain injury, minimal brain dysfunction, dyslexia, developmental aphasia), speech or language impairment, traumatic brain injury, visual impairment (including blindness), and developmental delay.

Dizziness
Physical unsteadiness, imbalance, and lightheadedness associated with balance disorders.

Due Process Complaint
A written complaint filed by a parent or a school district involving any matter relating to the identification, evaluation, educational placement or provision of a free and appropriate public education to a student with a disability. Due process complaints must be filed within two years of the matter in dispute.

Due Process Hearing
A formal, quasi-legal procedure before an impartial hearing officer or administrative law judge (or panel of judges) who is not an employee of the state educational agency or school district. Both the parents and the school district present arguments and evidence.

Dysarthria
Group of speech disorders caused by disturbances in the strength or coordination of the muscles of the speech mechanism as a result of damage to the brain or nerves.

Dysequilibrium
Any disturbance of balance.

Dysfluency
Disruption in the smooth flow or expression of speech.

Dysgeusia
Distortion or absence of the sense of taste.

Dyslexia
Learning disability characterized by reading difficulties. Some individuals may also have difficulty writing, spelling, or working with numbers.

Dysosmia
Distortion or absence of the sense of smell.

Dysphagia
Difficulty swallowing.

Dysphonia
Any impairment of the voice or speaking ability.

Dyspraxia of Speech
In individuals with normal muscle tone and speech muscle coordination, partial loss of the ability to consistently pronounce words.

Dystonia
Abnormal muscle tone of one or more muscles.