Glossary
Medical glossary A–Z
Plain-English definitions of the symptoms, conditions, tests, treatments and health-system terms people ask about most — each linked, where we cover it, to a fuller guide.
Medical language can put a barrier between people and their own health. This glossary explains 130+ of the terms that come up most often — across everyday symptoms and signs, disease and diagnosis, the body and physiology, common tests, treatments and medicines, and the digital-health and assurance standards we work with. Definitions are deliberately concise; where we have a fuller page on the topic, follow the link to read more.
A
- Acute
- Coming on quickly and usually lasting a short time. The opposite of chronic — it describes the speed of onset, not how serious something is. General & disease terms
- Acute-on-chronic
- A sudden worsening (acute flare) on top of a long-standing (chronic) condition — for example an acute chest infection in someone with chronic lung disease. General & disease terms
- Adherence · compliance
- How closely someone takes a medicine as prescribed. Also called compliance or concordance. Treatment & medicines
- Ambient scribe
- An AI tool that listens to a clinical encounter and drafts documentation; needs safety and DPIA evaluation before adoption. Digital health, assurance & interoperability
- Analgesic · painkiller
- A painkiller — a medicine that relieves pain, such as paracetamol or ibuprofen. Treatment & medicines
- Anorexia
- Loss of appetite. (Distinct from anorexia nervosa, which is an eating disorder.) Signs & symptoms
- Anti-inflammatory
- A medicine that reduces inflammation, swelling and pain — such as the NSAIDs ibuprofen and naproxen. Read more → Treatment & medicines
- Antibiotic
- A medicine that kills bacteria or stops them growing, used to treat bacterial infections. Antibiotics do not work against viruses. Treatment & medicines
- Antibody
- A protein made by the immune system that recognises and helps neutralise a specific germ or foreign substance. Body & physiology
- Anticoagulant · blood thinner
- A medicine that reduces the blood’s ability to clot ("blood thinner"), used to prevent or treat harmful clots. Treatment & medicines
- Ascites
- A build-up of fluid in the abdomen (tummy), often related to liver disease, causing swelling and discomfort. Signs & symptoms
- Atrophy
- Wasting or shrinking of a tissue or organ, such as muscle wasting from disuse. Body & physiology
B
- Baseline
- A person’s starting measurement, recorded so later results can be compared against it. Tests & investigations
- Benign
- Not cancerous, and not able to spread to other parts of the body. A benign growth may still need treatment if it causes symptoms, but it is not malignant. General & disease terms
- Benign tumour
- A non-cancerous growth that does not spread to other parts of the body, though it may still need removal if it presses on nearby structures. Body & physiology
- Benign vs malignant
- Benign means not cancerous and unable to spread; malignant means cancerous and able to spread. The distinction guides how urgently and how aggressively something is treated. General & disease terms
- Bilirubin
- A yellow substance from the breakdown of red blood cells; a raised level causes jaundice and can indicate a liver or blood problem. Tests & investigations
- Biopsy
- Taking a small sample of tissue so it can be examined under a microscope, usually to check for disease such as cancer. Read more → Tests & investigations
- Blood test
- A test on a sample of blood, analysed in a laboratory in many different ways depending on what the doctor is looking for. Read more → Tests & investigations
- Bradycardia
- A slower-than-normal resting heart rate, generally below 60 beats per minute in adults. It can be normal in fit people or a sign of a problem. Signs & symptoms
C
- Cardiovascular
- Relating to the heart and blood vessels. Body & physiology
- Chronic
- Long-lasting or persistent, usually meaning three months or more. A chronic condition is ongoing and managed over time rather than cured quickly. General & disease terms
- Clinical audit
- A cycle that measures practice against a defined standard, implements change, then re-measures to check for improvement. Medical education & exams
- Clinical safety case
- A structured, evidenced argument that a health IT system is acceptably safe for its intended use, owned by a Clinical Safety Officer. Digital health, assurance & interoperability
- Clinical Safety Officer (CSO)
- A suitably qualified clinician accountable for clinical risk management of a health IT system under DCB0129/0160, who owns the clinical safety case and hazard log. Digital health, assurance & interoperability
- Comorbidity
- Another long-term condition present at the same time as the main one — for example, having both diabetes and high blood pressure. General & disease terms
- Congenital
- Present from birth. A congenital condition may be inherited or may have developed during pregnancy. General & disease terms
- Contraindication
- A reason not to use a particular treatment because it could be harmful for that person — for example a drug that is unsafe in pregnancy. Treatment & medicines
- CT scan
- Computed tomography — a scan that combines many X-ray images into detailed cross-sectional "slice" pictures of the body. Read more → Tests & investigations
- Cyanosis
- A bluish colour of the skin or lips caused by low oxygen in the blood. Signs & symptoms
D
- DCB0129
- The clinical risk management standard for the manufacturer of a health IT system; produces a clinical safety case and hazard log. Digital health, assurance & interoperability
- DCB0160
- The clinical risk management standard for the healthcare organisation deploying a health IT system; manages local clinical risk. Digital health, assurance & interoperability
- Diagnosis
- Identifying the condition causing someone’s symptoms, from the history, examination and any test results. General & disease terms
- Differential (diagnosis)
- The ranked list of conditions that could explain a patient’s presentation, worked through with tests and examination — a core clinical-reasoning skill. Medical education & exams
- Differential diagnosis
- The list of possible conditions that could explain a person’s symptoms, which the doctor narrows down with examination and tests. General & disease terms
- dm+d
- Dictionary of Medicines and Devices — the UK standard terminology for medicines and medical devices, used for safe, consistent prescribing and data exchange. Digital health, assurance & interoperability
- Dose
- The amount of a medicine taken at one time; the dosage is how much and how often it is taken. Treatment & medicines
- DPIA
- Data Protection Impact Assessment — required under UK GDPR for high-risk processing, including most health AI. Digital health, assurance & interoperability
- DSP Toolkit
- Data Security and Protection Toolkit — the annual UK health-system data-security self-assessment for organisations handling health data or systems. Digital health, assurance & interoperability
- DTAC
- Digital Technology Assessment Criteria — the UK health-system baseline assessment across clinical safety, data protection, technical security, interoperability and usability/accessibility. Digital health, assurance & interoperability
- Dysphagia
- Difficulty swallowing, which should always be assessed as it can have several causes. Signs & symptoms
- Dyspnoea · breathlessness
- The medical term for breathlessness or shortness of breath. Read more → Signs & symptoms
- Dysuria
- Pain, stinging or burning when passing urine, commonly from a urine infection. Signs & symptoms
E
- ECG · EKG
- Electrocardiogram — a recording of the heart’s electrical activity, used to check its rhythm and look for strain or damage. Read more → Tests & investigations
- Endoscopy
- Looking inside the body using a thin, flexible tube with a camera — for example to examine the stomach or bowel. Read more → Tests & investigations
- Erythema
- Redness of the skin caused by increased blood flow, for example in inflammation or infection. Signs & symptoms
F
- False negative
- A test that wrongly shows a condition is absent when it is actually present. Tests & investigations
- False positive
- A test that wrongly shows a condition is present when it is not. Tests & investigations
- FHIR
- Fast Healthcare Interoperability Resources — a modern, web-API standard for exchanging health data. Digital health, assurance & interoperability
- Formulary
- An approved list of medicines that clinicians in a particular area or hospital are recommended to prescribe. Treatment & medicines
- Full blood count · FBC
- A common blood test that measures red cells, white cells and platelets — used to check for anaemia, infection and many other problems. Read more → Tests & investigations
G
- Gastrointestinal · GI
- Relating to the stomach and intestines — the digestive tract. Body & physiology
- Generic medicine
- A medicine sold under its active-ingredient name rather than a brand name, usually cheaper but equivalent in effect. Treatment & medicines
- GMC
- General Medical Council — the body that registers and regulates doctors in the UK and sets the standards they must meet. Medical education & exams
H
- Haematuria · blood in urine
- Blood in the urine, which may be visible or found only on testing. It always needs assessment. Signs & symptoms
- Haemoptysis
- Coughing up blood or blood-stained mucus from the airways or lungs. Signs & symptoms
- Hazard log
- A living record of identified clinical hazards, their risk ratings and the controls that mitigate them, maintained as part of clinical risk management. Digital health, assurance & interoperability
- Hepatic
- Relating to the liver. Body & physiology
- Hereditary · genetic, inherited
- Passed from parents to children through genes. Also called genetic or inherited. General & disease terms
- HL7 v2
- A long-established health-messaging standard widely used across hospital and laboratory systems. Digital health, assurance & interoperability
- Hormone
- A chemical messenger released into the blood by a gland that controls processes such as growth, metabolism and reproduction. Body & physiology
- Hyperglycaemia · high blood sugar
- A higher-than-normal level of glucose (sugar) in the blood, common in diabetes. Body & physiology
- Hypertension · high blood pressure
- Persistently raised blood pressure, which increases the long-term risk of stroke, heart attack and kidney disease. Read more → Body & physiology
- Hypertrophy
- Enlargement of a tissue or organ because its cells grow bigger — for example heart-muscle thickening. Body & physiology
- Hypoglycaemia · low blood sugar
- A lower-than-normal level of blood glucose, which can cause shakiness, sweating and confusion and needs prompt treatment. Body & physiology
- Hypotension · low blood pressure
- Blood pressure that is lower than normal, which can cause dizziness or fainting if it drops too far. Body & physiology
- Hypoxia
- Too little oxygen reaching the body’s tissues. Body & physiology
I
- Idiopathic
- Arising on its own with no identifiable cause. "Idiopathic" simply means the reason is unknown. General & disease terms
- Immune system
- The network of cells and organs that defends the body against infection and disease. Body & physiology
- Immunisation · vaccination
- Protecting a person against a disease, usually by vaccination, so the immune system can fight it off in future. Treatment & medicines
- Incidence
- How many new cases of a condition appear in a population over a set period, such as a year. General & disease terms
- Infarction
- Death of tissue because its blood supply has been cut off — as in a heart attack (myocardial infarction). Body & physiology
- Inflammation
- The body’s natural response to injury or infection — redness, heat, swelling and pain as the immune system reacts and repairs. Body & physiology
- Intended use
- The precise statement of what a product does, for whom and in what setting. Clear intended use scopes regulatory, clinical-safety and procurement assessment. Digital health, assurance & interoperability
- Intravenous · IV
- Given directly into a vein, usually through a drip or injection. Treatment & medicines
- Ischaemia
- A reduced blood supply to a part of the body, which starves the tissue of oxygen and can cause pain or damage. Body & physiology
J
- Jaundice
- Yellowing of the skin and the whites of the eyes, caused by a build-up of bilirubin, often signalling a liver, bile-duct or blood problem. Signs & symptoms
L
- Lesion
- Any area of abnormal tissue or damage — a broad term covering wounds, ulcers, growths and more. Body & physiology
- Lethargy · fatigue
- A state of tiredness, low energy and reduced alertness. Read more → Signs & symptoms
M
- Malaise
- A general feeling of being unwell, "off colour" or lacking energy, often an early and non-specific sign of illness. Signs & symptoms
- Malignant
- Cancerous — able to invade nearby tissue and spread (metastasise) to other parts of the body. General & disease terms
- Metabolism
- All the chemical processes that keep the body working — turning food into energy and building or repairing tissue. Body & physiology
- Metastasis · secondary, mets
- The spread of cancer from where it started to a new part of the body, forming a secondary tumour. General & disease terms
- MHRA
- Medicines and Healthcare products Regulatory Agency — the UK regulator overseeing medicines and medical devices, including software classified as a medical device. Digital health, assurance & interoperability
- MRI scan
- Magnetic resonance imaging — a scan that uses a strong magnetic field and radio waves to create detailed images, especially of soft tissues. Read more → Tests & investigations
N
- Nausea
- The feeling of being about to be sick (vomit). Signs & symptoms
- Neurological
- Relating to the brain, spinal cord and nerves. Body & physiology
O
- Oedema · edema, fluid retention
- Swelling caused by fluid building up in the body’s tissues, often seen in the ankles, legs or feet. Signs & symptoms
- Oedema (pulmonary)
- Fluid collecting in the lungs, causing breathlessness — often a sign that the heart is not pumping effectively. Body & physiology
- Oncology
- The branch of medicine concerned with diagnosing and treating cancer. Body & physiology
- Oral
- Taken by mouth — for example a tablet, capsule or liquid that is swallowed. Treatment & medicines
- OSCE
- Objective Structured Clinical Examination — a circuit of timed stations assessing clinical and communication skills. Medical education & exams
P
- Palliative care
- Care that focuses on relieving symptoms and improving quality of life in serious illness, alongside or instead of treatments aimed at cure. General & disease terms
- Palpitations
- An awareness of your own heartbeat — feeling it racing, pounding, fluttering or skipping. Read more → Signs & symptoms
- Paraesthesia · pins and needles
- Abnormal skin sensations such as tingling, prickling or "pins and needles", often from nerve irritation. Read more → Signs & symptoms
- PDSA cycle
- Plan-Do-Study-Act — the core quality-improvement loop: plan a small change and predict its effect, do it on a small scale, study the result, then act. Medical education & exams
- Photophobia
- Discomfort or pain in the eyes on exposure to light, which can accompany migraine, eye problems or meningitis. Signs & symptoms
- PLAB
- Professional and Linguistic Assessments Board — the established route for international medical graduates to GMC registration. Medical education & exams
- Placebo
- A dummy treatment with no active ingredient, used in trials to compare against a real medicine. Treatment & medicines
- Positive result
- A test result showing that what was being looked for is present. Whether that is good or bad news depends entirely on the test. Tests & investigations
- Prevalence
- How common a condition is in a population at a given time — the proportion of people who have it. General & disease terms
- Prognosis
- The likely course and outcome of a condition — a doctor’s best estimate of what to expect, based on the diagnosis and other factors. General & disease terms
- Prophylaxis · preventive treatment
- Treatment given to prevent a problem before it happens, rather than to treat an existing one — for example antibiotics before certain surgery. Treatment & medicines
- Pruritus · itch
- The medical term for itching. Signs & symptoms
- Pyrexia · fever
- The medical term for a raised body temperature, or fever. Read more → Signs & symptoms
Q
- Quality Improvement (QI)
- Iterative testing of small changes (for example PDSA cycles) to improve a process over time. Medical education & exams
R
- Reference range · normal range
- The range of values considered normal for a blood or other test. A result just outside the range is not always a problem and is read alongside symptoms. Tests & investigations
- Relapse · flare, recurrence
- The return of a disease or its symptoms after a period of improvement or remission. General & disease terms
- Remission
- A period when the signs and symptoms of a disease are reduced or gone. Remission is not always the same as cure — the condition can return. General & disease terms
- Renal
- Relating to the kidneys. Body & physiology
- Respiratory
- Relating to breathing and the lungs and airways. Body & physiology
- Risk factor
- Something that increases the chance of developing a condition — such as smoking for heart disease. Having a risk factor does not guarantee the disease. General & disease terms
- RWD
- Real-World Data — the raw data from routine care (records, registries, claims) that, once analysed, becomes real-world evidence. Digital health, assurance & interoperability
- RWE
- Real-World Evidence — clinical evidence generated from routine-care data (electronic records, registries) rather than only trials. Digital health, assurance & interoperability
S
- SaMD
- Software as a Medical Device — software with a medical purpose that may be regulated as a medical device by the MHRA. Digital health, assurance & interoperability
- Screening
- Testing people who have no symptoms to find a condition early, when treatment is more likely to work — for example cervical or bowel screening. Tests & investigations
- Side effect · adverse effect
- An unwanted effect of a medicine that happens alongside its intended action. Treatment & medicines
- SNOMED CT
- A comprehensive clinical terminology used across UK health systems to code diagnoses, findings and procedures so clinical meaning is shared consistently between systems. Digital health, assurance & interoperability
- Steroid · corticosteroid
- A medicine (corticosteroid) that reduces inflammation and calms the immune system, used in conditions such as asthma, eczema and arthritis. Treatment & medicines
- Syncope · fainting
- The medical word for fainting — a brief loss of consciousness caused by a temporary drop in blood flow to the brain. Read more → Signs & symptoms
- Syndrome
- A recognised group of symptoms and signs that tend to occur together, even when the single underlying cause is not fully known. General & disease terms
T
- Tachycardia
- A faster-than-normal resting heart rate, generally above 100 beats per minute in adults. Read more → Signs & symptoms
- Terminal
- A condition that cannot be cured and is expected to lead to death, where care focuses on comfort and quality of life. General & disease terms
- Titration
- Gradually adjusting a medicine’s dose up or down to find the amount that works best with fewest side effects. Treatment & medicines
- Topical
- Applied directly to the skin or surface of the body, such as a cream or ointment. Treatment & medicines
U
- UK GDPR
- The UK data-protection regime that, with the Data Protection Act, governs processing of personal data — including the DPIA requirement for high-risk processing such as most health AI. Digital health, assurance & interoperability
- UKMLA
- UK Medical Licensing Assessment — the GMC common assessment (Applied Knowledge Test plus Clinical and Professional Skills Assessment). Medical education & exams
- Ultrasound
- A scan that uses sound waves to build real-time images of organs and structures, with no radiation. Read more → Tests & investigations
V
- Vertigo
- A false sense that you or your surroundings are spinning or moving, usually from a problem in the inner ear or balance system. Read more → Signs & symptoms
X
- X-ray
- An imaging test using small doses of radiation to show dense structures such as bones. Read more → Tests & investigations
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