Glossary

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Activities of daily living(also: ADLs, Daily living activities)

The fundamental self-care tasks that a person performs routinely each day, including feeding, bathing, dressing, grooming, toileting, and mobility. Originally proposed by Sidney Katz in the 1950s, ADLs are used in healthcare and occupational therapy as a measure of functional…

Adventitious blindness(also: Acquired blindness, Late blindness, Acquired visual impairment)

Vision loss that occurs after a period of sighted experience, as opposed to congenital blindness (present from birth). People with adventitious blindness retain visual memories, mental imagery, and familiarity with visual concepts like color and spatial layout, which…

Age-Related Capability Decline(also: Age-Related Impairment, Dynamic Diversity)

The gradual reduction in sensory, motor, and cognitive capabilities that typically accompanies ageing, including declining visual acuity, hearing loss, reduced dexterity and fine motor control, and changes in memory and processing speed. Unlike many disabilities that are stable…

Age-Related Decline(also: Age-Related Impairment, Age-Related Changes)

The gradual reduction in physical, sensory, and cognitive abilities that occurs as part of the natural aging process. Age-related declines that affect technology use include reduced visual acuity (difficulty reading small text and icons), decreased fine motor control (difficulty…

Agnosia

A neurological condition in which a person has difficulty recognising familiar objects, faces, places, sounds, or other sensory stimuli despite intact basic sensory function and general cognition. Specific subtypes include visual agnosia (difficulty recognising objects or…

Alexithymia

A subclinical condition in which a person has marked difficulty identifying, describing, and distinguishing their own emotions, often accompanied by an externally oriented thinking style and limited imagination about inner states. Alexithymia commonly co-occurs with autism,…

Amblyopia(also: Lazy eye)

A neurodevelopmental vision disorder in which one eye has reduced visual acuity that cannot be fully corrected with glasses or contact lenses, caused by abnormal visual development in early childhood. The brain favors one eye and partially suppresses input from the weaker eye,…

Anomalous Trichromacy(also: Anomalous Trichromatic Vision)

A category of colour vision deficiency where all three types of cone cells are present but one type has a shifted sensitivity range, resulting in altered colour perception that is less severe than dichromacy. The three forms are protanomaly (shifted red cones), deuteranomaly…

Anomia(also: Word-finding difficulty, Anomic aphasia)

Anomia is a language impairment characterized by difficulty retrieving words during speech, particularly the names of objects, people, or actions. It is the most common symptom across all types of aphasia and can also occur as a standalone condition (anomic aphasia). In…

Anxiety(also: Anxiety Disorder)

An emotional and physiological state characterised by apprehension about future threats, accompanied by heightened autonomic arousal (elevated heart rate, muscle tension, shallow breathing), attentional bias toward danger cues, and often avoidance behaviour. Clinical anxiety…

Aphantasia(also: Mind Blindness)

Aphantasia is a neurological condition in which a person is unable to voluntarily create mental images or visualize objects, people, or scenes in their mind. It affects an estimated 2-5% of the population and exists on a spectrum from reduced imagery to complete absence. In…

Apraxia(also: Apraxia of Speech, Childhood Apraxia of Speech, CAS)

A motor speech disorder in which the brain has difficulty coordinating the muscle movements needed to produce speech, despite the muscles themselves not being weak. The person knows what they want to say but their brain has difficulty planning and sequencing the precise…

Astigmatism

A common refractive error caused by an irregularly shaped cornea or lens, resulting in blurred or distorted vision at all distances. The cornea is shaped more like a rugby ball than a sphere, causing light to focus on multiple points rather than one. Astigmatism frequently…

AuDHD(also: Autism and ADHD co-occurrence)

A term used by the neurodivergent community to describe the co-occurrence of autism spectrum disorder and attention deficit hyperactivity disorder in the same individual. Research suggests significant overlap between the two conditions, with estimates indicating that 50-70% of…

Auditory processing disorder(also: APD, Central auditory processing disorder, CAPD)

A neurological condition in which the brain has difficulty interpreting and organizing sounds despite normal hearing ability. Unlike hearing loss, auditory processing disorder affects how the central auditory nervous system processes what is heard, making it difficult to…

Autistic Burnout(also: Autistic Fatigue, Neurodivergent Burnout)

A state of physical, mental, and emotional exhaustion experienced by autistic people, often resulting from the cumulative effect of masking (suppressing autistic traits to appear neurotypical), sensory overload, and the ongoing effort of navigating environments not designed for…

Autistic Meltdown(also: Meltdown, Sensory Meltdown)

An autistic meltdown is an intense, involuntary response to overwhelming sensory, emotional, or cognitive overload, during which an autistic person may temporarily lose the ability to regulate their behavior, emotions, or communication. Meltdowns can manifest as crying, shutting…

Blindness(also: Blind, Total Blindness, Complete Vision Loss)

A condition characterised by the complete or near-complete absence of functional vision, ranging from no light perception to minimal light awareness that cannot be used for practical tasks. Blind individuals typically rely on non-visual senses and assistive technologies such as…

Brain Fog(also: Cognitive Fog, Mental Fog)

Brain fog is a term used to describe a cluster of cognitive symptoms including difficulty concentrating, memory problems, mental fatigue, and reduced clarity of thought. It is commonly associated with chronic conditions such as fibromyalgia, multiple sclerosis, long COVID,…

Central Vision Loss(also: Central Field Loss, Central Scotoma)

Loss of vision in the central part of the visual field, typically caused by damage to the macula — the area of the retina responsible for sharp, detailed vision. People with central vision loss experience difficulty seeing fine details directly in front of them, often describing…

Cerebral Visual Impairment(also: CVI, Cortical Visual Impairment)

Cerebral visual impairment (CVI) is an umbrella term for visual deficits resulting from damage to the brain rather than the eyes. It affects visual perception, including visual acuity, cortical image processing, and pattern recognition. CVI is often associated with additional…

Clinical Dementia Rating(also: CDR, CDR Scale)

The Clinical Dementia Rating (CDR) is a five-point staging scale used to characterise the severity of dementia, originally developed by Hughes and colleagues at Washington University in 1982. A clinician rates the person across six domains — memory, orientation, judgement and…

Cochlear implant(also: CI, Bionic ear)

A surgically implanted electronic device that provides a sense of sound to a person with severe to profound sensorineural hearing loss by directly stimulating the auditory nerve, bypassing damaged hair cells in the cochlea. Unlike hearing aids, which amplify sound, cochlear…

Cognitive load(also: Mental load, Cognitive burden, Cognitive demand)

The total amount of mental effort required to complete a task, encompassing the processing of information, decision-making, remembering instructions, and managing attention. Cognitive load theory, developed by John Sweller in the 1980s, distinguishes between intrinsic load…

Cognitive-Communication Needs(also: CCN, Cognitive-Communication Disorders)

Difficulties in communication that arise from underlying cognitive deficits in areas such as attention, memory, organization, problem-solving, and executive function, rather than from primary language impairments. Cognitive-communication needs commonly result from traumatic…

Colour Vision Deficiency(also: CVD, Color Blindness, Colour Blindness)

A condition in which a person has difficulty distinguishing between certain colours due to differences in the cone cells of the retina. CVD affects approximately 1 in 12 men and 1 in 200 women worldwide. It is not typically a complete inability to see colour but rather a reduced…

Convergence Insufficiency(also: CI)

A binocular vision disorder in which the eyes have difficulty turning inward (converging) to focus on nearby objects, causing symptoms such as double vision, eye strain, headaches, difficulty reading, and blurred vision during close work. Convergence insufficiency affects an…

Cortical visual impairment(also: CVI, Cerebral visual impairment)

A neurological form of visual impairment caused by damage or atypical structures in the visual pathways and visual processing centres of the brain, rather than in the eyes themselves. CVI is now the most common cause of visual impairment in children in developed countries.…

Deafblind(also: Deaf-Blind, Deafblindness, Dual Sensory Loss)

A condition involving combined hearing and vision loss that significantly affects communication, access to information, and mobility. Deafblindness is not simply the sum of deafness and blindness — it creates unique challenges that require distinct support strategies, including…

Deafblindness(also: Deaf-Blindness, Dual Sensory Impairment, Combined Vision and Hearing Loss)

Deafblindness is a combined vision and hearing impairment that creates unique challenges beyond those associated with either sensory loss alone. It is not simply the sum of deafness and blindness — the combination creates distinct communication, information access, and mobility…

Decreased Sound Tolerance(also: DST, Sound Intolerance)

Decreased sound tolerance (DST) is an umbrella term for conditions in which everyday sounds are perceived as uncomfortably loud, threatening, or emotionally distressing. It encompasses hyperacusis (abnormal sensitivity to sound volume), misophonia (strong emotional reactions to…

Dementia(also: Major neurocognitive disorder)

An umbrella term for a group of symptoms related to progressive decline in memory, thinking, behaviour, and the ability to perform everyday activities, caused by diseases or injuries affecting the brain. Alzheimer's disease is the most common cause, accounting for 60-70% of…

Deuteranomaly(also: Deutan Anomalous Trichromacy)

The most common type of colour vision deficiency, where the medium-wavelength (green) cone cells have a shifted sensitivity range. Deuteranomaly is a milder form of deutan CVD compared to deuteranopia, resulting in reduced ability to distinguish certain reds from greens. It…

Deuteranopia(also: Deutan Dichromacy, Green-Blind)

A type of colour vision deficiency caused by the complete absence of medium-wavelength (green) cone cells in the retina. Deuteranopia is the most common form of dichromacy, causing difficulty distinguishing red from green. Unlike protanopia, deuteranopia does not significantly…

Developmental Learning Disorder(also: DLD, Specific Learning Disorder, Learning Disability)

A group of neurodevelopmental conditions that affect the acquisition and use of specific academic skills such as reading, writing, or mathematics. Developmental Learning Disorders include dyslexia (affecting reading), dysgraphia (affecting writing), and dyscalculia (affecting…

Dichromacy(also: Dichromatic Vision)

A category of colour vision deficiency in which one of the three types of cone cells is completely absent, reducing colour perception to two primary channels instead of three. The three forms are protanopia (missing red cones), deuteranopia (missing green cones), and tritanopia…

Digital accessibility for ageing(also: Age-related accessibility, Accessible ageing, Senior accessibility)

The practice of designing digital technologies that remain usable as people experience age-related changes in vision (presbyopia, contrast sensitivity loss, cataracts), hearing (presbycusis), motor control (reduced dexterity, tremor), cognition (slower processing, working memory…

Disordered Speech(also: Pathological Speech, Atypical Speech)

Speech that differs from typical patterns due to motor, neurological, structural, or developmental conditions. Disordered speech encompasses conditions like dysarthria, apraxia, stuttering, and speech differences from cerebral palsy or Parkinson's disease. For accessibility,…

Drop Foot(also: Foot Drop, Peroneal Nerve Palsy)

A condition characterized by difficulty lifting the front part of the foot, causing the toes to drag along the ground during walking. Drop foot is not a disease itself but a symptom of an underlying neurological, muscular, or anatomical problem, commonly caused by nerve injury…

Duchenne Muscular Dystrophy(also: DMD, Duchenne MD)

Duchenne Muscular Dystrophy (DMD) is a severe genetic disorder characterized by progressive muscle degeneration and weakness, caused by mutations in the dystrophin gene on the X chromosome. It primarily affects boys, with symptoms typically appearing between ages 2-5 and…

Dysarthria(also: Motor speech disorder, Neuromotor speech impairment)

A group of speech disorders caused by weakness, paralysis, or lack of coordination in the muscles used for speaking, resulting from damage to the brain or nervous system. Speech may sound slurred, slow, or difficult to understand, though the person's language comprehension and…

Dyscalculia(also: Math Learning Disability, Number Blindness, Mathematics Disorder)

A specific learning disorder that affects the ability to acquire, understand, and manipulate numerical and mathematical concepts. People with dyscalculia may have difficulty with number sense, memorizing arithmetic facts, performing calculations, and understanding mathematical…

Dysgraphia(also: Disorder of written expression, Specific learning disorder in written expression)

A neurological learning disability that affects written expression, including handwriting legibility, spelling accuracy, and the ability to organize thoughts in writing. Dysgraphia can make text entry and written composition cognitively exhausting, creating significant barriers…

Dyspraxia(also: Developmental Coordination Disorder, DCD)

A neurodevelopmental condition affecting motor planning, coordination, and the sequencing of movements. People with dyspraxia have difficulty translating intended actions into coordinated physical movements, despite having adequate muscle strength and understanding of what they…

Early-Onset Dementia(also: Young-Onset Dementia, Working-Age Dementia)

Dementia diagnosed before the age of 65, affecting individuals who are often still in the workforce and digitally active. Early-onset dementia presents unique accessibility challenges because affected individuals typically have established digital literacy and strong…

Epilepsy(also: Seizure Disorder)

A chronic neurological condition characterized by recurrent, unprovoked seizures caused by abnormal electrical activity in the brain. Epilepsy affects roughly 1% of the population globally and spans a wide range of seizure types and severities, with some people experiencing…

Essential Tremor(also: ET, Benign Essential Tremor)

Essential tremor is one of the most common movement disorders, characterized by involuntary, rhythmic shaking that typically affects the hands and arms but can also involve the head, voice, and other body parts. Unlike Parkinson's disease tremor, essential tremor usually occurs…

Facial Palsy(also: Bell's Palsy, Facial Paralysis, Unilateral Facial Palsy)

Facial palsy is a condition involving weakness or paralysis of the facial muscles, typically caused by damage to the facial nerve (cranial nerve VII). Bell's palsy is the most common form, appearing suddenly and usually affecting one side of the face. Facial palsy can…

Fibromyalgia(also: FM, Fibromyalgia syndrome)

Fibromyalgia is a chronic condition characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and cognitive difficulties often called "fibro fog." It affects approximately 2-4% of the population, predominantly women, and is considered an invisible disability…

Fine Motor Function(also: Fine Motor Control, Fine Motor Skills, LFMF)

The ability to make precise, coordinated movements using the small muscles of the hands and fingers. Fine motor function is essential for touch screen interaction, including tapping specific targets, typing on virtual keyboards, and performing gestures like swiping and pinching.…