Words on this site, in plain English
Written by AI from saved sources. A script checks every quote word for word, and a second AI compares each claim with its source. How we work and corrections
This page gives short meanings of words our pages use. Each meaning comes from a named dictionary, health body or encyclopedia, with a link to the source.
A
Acceptable daily intake — An estimate of how much of a substance in food or drinking water can be consumed every day for a lifetime without a significant risk to health. It applies to chemicals such as food additives, pesticide residues and veterinary drugs, and is usually given in milligrams per kilogram of body weight per day.
Source: EFSA, Glossary A (undated)
Acid reflux — Stomach acid travelling up towards the throat. If it keeps happening, it may be called gastro-oesophageal reflux disease (GORD).
Acute — Sudden: symptoms appear, change or get worse quickly.
Adverse event — An unwanted medical event in a trial participant given the treatment being studied. The treatment need not have caused it.
Antibiotic — A medicine that fights bacterial infections in people and animals by killing bacteria or making it hard for them to grow and multiply. Antibiotics do not work on viral infections.
Source: MedlinePlus, Antibiotics (2023)
Antibody — A protein found in blood, produced in response to foreign substances such as bacteria or viruses invading the body.
Source: CDC, Vaccine Glossary (2024)
B
Benzene — A chemical that is a colourless or light-yellow liquid at room temperature.
Source: CDC, Benzene (2026)
Bias — A consistent tendency in how research is done or reviewed that can lead results or conclusions away from the truth; it need not be deliberate. Cochrane uses “risk of bias” for limitations in how studies are designed and carried out.
Source: CDC, Principles of Epidemiology: Glossary (2014); Cochrane, Chapter 14: Completing ‘Summary of findings’ tables and grading the certainty of the evidence (2024)
Biotechnology — Broadly, the use of biology in technology. In common US food usage, it means foods produced using recombinant DNA: techniques that change genetic material to achieve a desired trait.
C
Calorie — A unit of energy in food.
Source: NIDDK, via MedlinePlus, Definitions of Health Terms: Nutrition (undated)
Carbohydrate — One of the main types of nutrients. Digestion changes carbohydrates into glucose (blood sugar), which the body uses for energy.
Source: NIH MedlinePlus, Definitions of Health Terms: Nutrition (undated)
Carcinogenic — Able to cause cancer when a human or animal is exposed to the substance.
Source: EFSA, Glossary C (undated)
Central nervous system — The brain and spinal cord.
Source: A.D.A.M., via MedlinePlus, Central nervous system (2025)
Certainty of evidence — In systematic reviews, GRADE certainty describes how confident researchers can be that an estimate of an effect or link is close to the value they want to measure. It is assessed for each outcome.
Chemotherapy — Cancer treatment using medicines to destroy cancer cells. It can kill the cells, stop them spreading or slow their growth.
Cholesterol — A waxy, fat-like substance found in all cells of the body.
Source: NHLBI, via MedlinePlus, Definitions of Health Terms: Nutrition (undated)
Cohort — A clearly defined group of people who share an experience or exposure and are followed over time to find new diseases or health events.
Complementary — A healthcare approach outside mainstream medicine that is used alongside conventional medicine. An approach used in place of conventional medicine is called “alternative”.
Source: NCCIH, Complementary, Alternative, or Integrative Health: What’s In a Name? (2021)
Confidence interval — A 95% confidence interval comes from a method that, over repeated samples from the same population, gives ranges containing the true value of an association 95% of the time. It measures precision, without addressing bias.
Convenience sampling — Choosing a sample based on availability, opportunity or convenience, without using random selection.
Source: CDC, Sampling Methodology (2024)
Correlation — A statistical measure of the form, direction and strength of a relationship between two things.
D
Dehydration — A condition that happens when you do not take in enough liquid to replace what you lose.
Source: MedlinePlus, Definitions of Health Terms: Nutrition (undated)
DNA — The material that carries inherited information in humans and almost all other living things.
Double-blind — Usually means that trial participants and researchers do not know which treatment each participant has been assigned. Where appropriate, other staff at the research site or working for the trial sponsor are also kept unaware.
Drug interaction — A change in how a drug acts in the body when taken with certain other drugs, foods or supplements. This can also happen when someone takes a drug while they have certain medical conditions.
E
Electrolyte — A mineral in body fluids, such as sodium, potassium, magnesium or chloride.
Source: MedlinePlus, Definitions of Health Terms: Nutrition (undated)
Electrolyte imbalance — When the level of one or more electrolytes in your body is too low or too high.
Enteric-coated — Describes tablets with a coating that delays release of the medicine until after they leave the stomach.
Enzyme — A substance that speeds up chemical reactions in the body.
Source: NIDDK, via MedlinePlus, Definitions of Health Terms: Nutrition (undated)
F
Frequency — How often an event repeats, measured in hertz (Hz): the number of events or cycles per second.
Functional magnetic resonance imaging (fMRI) — A specialised type of MRI that shows brain structures and identifies which brain areas use more oxygen during thinking tasks.
Source: NIH NIBIB, Magnetic Resonance Imaging (MRI) (undated)
G
Greenhouse gas — A gas in Earth’s atmosphere that contributes to the greenhouse effect by absorbing and emitting infrared radiation.
Source: NOAA GML, Education — Behind the Scenes: Glossary (undated)
H
Hazard — A substance or activity that could harm living things or the environment.
Source: EFSA, Glossary H (undated)
Herd immunity — When enough people are immune to an infectious disease through vaccination or previous illness to make spread from person to person unlikely. This offers some protection even to people who have not been vaccinated.
Source: CDC, Vaccine Glossary (2024)
I
Immune response — How the body recognises and defends itself against bacteria, viruses and substances that appear foreign and harmful.
Immune system — A network of cells, tissues and organs that work together to help the body fight infections and other diseases.
Immunocompromise — Having an immune system weakened by long-term illnesses, underlying health conditions or medicines.
Inactivated vaccine — A vaccine made from viruses or bacteria killed by physical or chemical processes, or from protein parts of infectious agents. The killed organisms cannot cause disease.
Source: CDC, Vaccine Glossary (2024)
Inflammation — The body’s response when tissues are injured by bacteria, physical injury, toxins, heat or other causes. Damaged cells release chemicals that make blood vessels leak fluid into the tissues, causing swelling.
Ion — An atom that has gained or lost one or more electrons and become electrically charged as a result.
Irritable bowel syndrome — Irritable bowel syndrome (IBS) affects the large intestine and can cause cramps in the belly, bloating and changes in bowel habits. It can cause a lot of discomfort, but it does not harm the intestines.
L
Laxative — A medicine that helps you poo.
Source: NHS, Laxatives (2026)
Log reduction — Each log of microbial kill means a tenfold reduction in the number of organisms the treatment targets. For example, FDA’s 5-log standard for juice means a process capable of reducing the target pathogen at least 100,000-fold.
M
Magnetic resonance imaging (MRI) — A way to make detailed three-dimensional images of body structures without entering the body.
Source: NIH NIBIB, Magnetic Resonance Imaging (MRI) (undated)
Median — The middle value that divides a set of data into two equal parts, with the same number of values above and below it.
Menopause — The time when periods stop and you can no longer get pregnant. You have reached menopause after 12 months without a period.
Source: MedlinePlus, Menopause (2026)
Messenger RNA (mRNA) — A type of single-stranded RNA made from a DNA template. It carries protein-making information from DNA in the cell’s nucleus to the cell’s watery interior, where that information is read to build a protein.
Source: NHGRI, Talking Glossary of Genomic and Genetic Terms (undated)
Meta-analysis — Combining the results of two or more separate studies using statistics. It can seriously mislead if study design, bias within studies, differences between studies and bias in reporting are not carefully considered.
Source: Cochrane, Chapter 10: Analysing data and undertaking meta-analyses (2024)
Misbranded — A US legal term for failures to meet drug or device labelling requirements, including false or misleading labelling or missing required warnings. Inadequate directions for over-the-counter drugs and devices also count; exemptions from the directions and warnings provision are possible.
Model — A representation of reality in physical, mathematical or logical form.
Molecule — A group of atoms held together by chemical forces.
Myocarditis — Inflammation of the heart muscle.
N
Nasal polyp — A soft, sac-like growth on the lining of the nose or sinuses. Nasal polyps are not cancer.
Natural immunity — Protection against a disease acquired through infection with the organism that causes it.
Source: CDC, Immunity Types (2024)
Neurodevelopmental disorder — A condition that begins during development, usually early in childhood. Problems with development interfere with personal or social life, school or work.
Neuron — A basic cell of nervous tissue that receives and passes on signals in the nervous system.
Source: NLM MeSH, Neurons (undated)
Nonadherent dressing — A wound covering that does not stick to fluid released from the wound.
Source: British Association of Dermatologists, Dermatology Handbook for Registrars (2020)
Nucleus — The part of a cell enclosed by a membrane that contains the chromosomes.
Source: NHGRI, Talking Glossary of Genomic and Genetic Terms (undated)
O
Observational study — A study in which researchers watch, rather than influence, what participants are exposed to and which diseases they have.
Odds — The chance of an event happening divided by the chance of it not happening. For example, a risk of 0.5 gives odds of 1.
Source: Cochrane, Chapter 6: Choosing effect measures and computing estimates of effect (2024)
Oppositional defiant disorder — A pattern of disobedient, hostile and defiant behaviour towards authority figures. For diagnosis, it must last at least six months, exceed normal childhood misbehaviour, differ from that of children of the same age and developmental level, and cause significant school or social problems.
Source: A.D.A.M., via MedlinePlus, Oppositional defiant disorder (2026)
Osteoporosis — A disease that makes bones weak and likely to break.
Source: MedlinePlus, Osteoporosis (2025)
Oxidation — “A chemical reaction in which oxygen bonds to an element or compound. By extension, a reaction in which one element or compound rises to a higher oxidation state while another drops to a lower oxidation state (the term is used in this sense even when no oxygen whatever is present).”
Source: NOAA Office of Response and Restoration, Glossary Terms (undated)
Oxidative stress — “A disturbance in the prooxidant-antioxidant balance in favor of the former, leading to potential damage.”
P
Parasite — A living thing that lives on or inside another living thing and gets food from it or at its expense.
Source: CDC, About Parasites (2024)
Partial-thickness burn — A burn that affects both the outer layer of skin and the layer underneath.
Pasteurisation — Removing disease-causing germs from milk by heating it to a high enough temperature for a certain length of time.
Source: CDC, Raw Milk (2025)
Peer review — In medical research, checking quality before publication. At Cochrane, this means giving feedback on its protocols and reviews before publication.
Source: Cochrane, Peer review by patients and the public (undated)
Pericarditis — Inflammation of the sac-like covering around the heart, called the pericardium.
Perspective — Creating a sense of depth and distance in a picture by making distant people and things look smaller than nearer ones.
Source: Oxford Advanced Learner’s Dictionary, Perspective, noun (undated)
Pertussis — An infectious disease caused by bacteria, with bouts of coughing sometimes followed by a crowing sound when breathing in. Also called whooping cough.
Source: CDC, Vaccine Glossary (2024)
pH — A measure of how acidic or basic water is, based on hydrogen ion activity: below 7 is acidic, 7 is neutral and above 7 is basic. A fall of one pH unit means ten times the hydrogen ion concentration.
Source: EPA, pH (2026)
Placebo — A dummy treatment used for comparison in a clinical trial. The comparison treatment, called a control, can also be a standard treatment already in use.
Source: NHS, Clinical trials (2022)
Polyunsaturated fat — A type of fat that is liquid at room temperature. Its two types of fatty acids are omega-6 and omega-3.
Source: NIDDK, via MedlinePlus, Definitions of Health Terms: Nutrition (undated)
Preservative — In vaccines, a substance that prevents microbes from growing.
R
Radiation — Energy that travels as waves or high-speed particles.
Radiation belt — A ring-shaped region around a planet where electrically charged particles, usually electrons and protons, are trapped.
Randomisation — Using chance to assign trial participants to groups receiving different treatments, to reduce bias.
Randomised controlled trial — A clinical trial in which people are assigned by chance to groups with different exposures or treatments.
Receptor-binding domain — A part of the S1 section of a coronavirus spike protein that plays a key role in helping the virus attach.
Source: NCBI Conserved Domain Database, SARS-CoV_Spike_S1_RBD (2021)
Reflector (lunar laser ranging) — In Apollo lunar laser ranging, a small array of mirrors on the Moon. Scientists on Earth aim lasers at it and time how long the beams take to return.
Relative humidity — The moisture in air as a percentage of the amount that would be present at saturation at that temperature. It depends on both moisture and temperature, so it does not by itself tell you the actual amount of moisture present.
Source: NOAA National Weather Service, Glossary: Relative Humidity (undated)
Risk — The chance that something, such as illness, injury or death, will happen within a specified time or age range.
S
Saturated fat — A type of fat that is solid at room temperature.
Source: NIDDK, via MedlinePlus, Definitions of Health Terms: Nutrition (undated)
Serum — The clear liquid that separates from blood after it has clotted completely. It is essentially blood plasma with fibrinogen removed during clotting.
Shielding — Material or a barrier that absorbs radiation and tends to protect people or materials from the effects of ionizing radiation.
Solar particle event — An eruption on the Sun that releases many energetic particles, mainly protons, over hours or days.
Source: NASA, THREE Glossary (2026)
Space geodesy — Measuring Earth’s size, shape, gravity field and rotation using measurements between instruments on the ground and objects in space.
Statistical significance — “Statistical significance is based on an estimate of the probability of the observed or a greater degree of association between independent and dependent variables occurring under the null hypothesis”
Systematic review — A review of all the research data and results about a particular question, using a consistent, organised method.
T
Tooth enamel — The hard surface of a tooth.
Toxin — A substance made by germs, plants or animals that is poisonous to humans. The term can also include some medicines that are helpful in small doses but poisonous in large amounts, metals such as lead and certain chemicals in the environment.
Transistor — A switch made from semiconductor material that turns on or off as voltage changes. Transistors can be combined to make complex devices.
V
W
Weight-related stigma — Discriminatory actions and beliefs directed at people because of their weight and size.
Source: World Obesity Federation, Obesity & Weight Stigma (undated)
Check it yourself
Does statistical significance alone establish cause and effect?
Show answer
Statistical significance alone does not establish a cause-and-effect association.
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