Medical cannabis glossary

73 terms defined in plain English, covering the plant and its chemistry, how the medicines act, how preparations are made, the law that governs them, and the clinical process around a prescription. No product is named, ranked or priced anywhere in it.

The plant and its chemistry

• Cannabinoid — A compound that acts on the body's cannabinoid receptors — whether made by the plant, made by the body, or made in a laboratory.
• Phytocannabinoid — A cannabinoid produced by a plant, as distinct from one made by the body or synthesised in a laboratory.
• Endocannabinoid — A cannabinoid produced by the human body itself, acting on the same receptors that plant cannabinoids act on.
• THC (tetrahydrocannabinol) — The principal intoxicating compound in cannabis, and the source of most of the therapeutic effects and most of the risks.
• CBD — A non-intoxicating cannabinoid. It does not produce a high at any dose, and acts largely through routes other than the cannabinoid receptors.
• CBG (cannabigerol) — A minor cannabinoid, non-intoxicating, and the chemical precursor from which THC and CBD are formed in the plant.
• CBN (cannabinol) — A mildly intoxicating cannabinoid formed as THC degrades with time, light and heat.
• CBC (cannabichromene) — A minor non-intoxicating cannabinoid, studied mostly in laboratory models of inflammation and pain.
• THCV (tetrahydrocannabivarin) — A cannabinoid structurally related to THC that appears to behave differently, including on appetite.
• Terpene — An aromatic compound found in many plants, responsible for characteristic smells — including those of cannabis.
• Flavonoid — A class of plant pigment compounds present in cannabis alongside cannabinoids and terpenes.
• Trichome — The resin-producing gland on the surface of the cannabis flower, where cannabinoids and terpenes are made and stored.
• Full-spectrum — A preparation containing the range of compounds extracted from the plant, including cannabinoids other than the principal one and terpenes.
• Broad-spectrum — A preparation containing a range of plant compounds but with one component, usually THC, removed or reduced.
• Isolate — A single cannabinoid purified from everything else in the plant.
• Cultivar — A cultivated plant variety. In cannabis it is the accurate term for what is popularly called a strain.

The body and how the medicines act

• Endocannabinoid system — The body's own signalling system of cannabinoid molecules, the receptors they act on, and the enzymes that build and break them down.
• CB1 receptor — The cannabinoid receptor found in high density in the brain and central nervous system.
• CB2 receptor — The cannabinoid receptor found mainly in immune cells and peripheral tissue rather than in the brain.
• Anandamide — One of the two principal endocannabinoids produced by the human body.
• 2-AG (2-arachidonoylglycerol) — The second of the two principal endocannabinoids, present in the brain at considerably higher concentrations than anandamide.
• Agonist — A substance that binds to a receptor and activates it. A partial agonist activates it incompletely.
• Bioavailability — The proportion of a dose that reaches the bloodstream in active form.
• First-pass metabolism — The breakdown of a swallowed drug by the liver before it reaches the general circulation.
• Half-life — The time taken for the amount of a drug in the body to fall by half.
• Titration — The process of starting a medicine below the expected effective level and increasing gradually until benefit appears or side effects set a ceiling.
• Tolerance — A reduced response to the same amount of a drug after repeated exposure.
• Dependence — Physical adaptation to a drug such that stopping produces withdrawal symptoms.
• Entourage effect — The hypothesis that the compounds in cannabis work better together than any of them does in isolation.

Preparations and how they are made

• Medical weed — An informal name for cannabis prescribed as a medicine. The formal UK term is a cannabis-based product for medicinal use.
• CBPM (cannabis-based product for medicinal use) — The UK regulatory category created in November 2018 for cannabis products that may be prescribed by a specialist.
• Unlicensed medicine — A medicine without a marketing authorisation from the MHRA for the use in question.
• Licensed medicine — A medicine granted a marketing authorisation by the MHRA for a specified use, having satisfied requirements on quality, safety and efficacy.
• Off-label — Use of a licensed medicine for a purpose, population or dose outside the terms of its licence.
• Special (unlicensed special) — A medicine manufactured or imported to meet the needs of an individual patient where no licensed product is suitable.
• Flos — The pharmaceutical term for dried cannabis flower prepared as a medicine.
• Granulate — Cannabis flower processed into a uniform granular form for medicinal use.
• Carrier oil — The oil in which cannabinoids are dissolved to make an oral or sublingual preparation.
• Excipient — Any component of a medicine other than the active substance.
• Sublingual — Administered under the tongue, where a drug is absorbed through the lining of the mouth.
• Oromucosal — Administered to the lining of the mouth generally, including under the tongue and inside the cheek.
• Vaporiser — A device that heats cannabis material enough to release its active compounds as vapour without burning it.
• Irradiation — Treatment of cannabis material with ionising radiation to reduce microbial contamination.
• Certificate of analysis — A laboratory document recording the verified content of a specific batch of a product.
• Batch number — The identifier linking a dispensed medicine to a specific production run.

Law and regulation

• Schedule 2 — The Misuse of Drugs Regulations schedule containing controlled drugs with recognised medical uses and strict handling requirements.
• Controlled drug — A substance regulated under the Misuse of Drugs Act 1971 and the Misuse of Drugs Regulations 2001.
• Misuse of Drugs Act 1971 — The primary UK legislation controlling dangerous or otherwise harmful drugs.
• Misuse of Drugs Regulations 2001 — The secondary legislation setting out how controlled drugs may lawfully be produced, supplied, prescribed and possessed.
• 28-day rule — A Schedule 2 prescription is valid for 28 days from the date on it, and prescribing is normally limited to 30 days' supply.
• Home Office personal licence — The licence required to carry three months' supply or more of a controlled drug into or out of the UK.
• MHRA — The Medicines and Healthcare products Regulatory Agency, the UK regulator for medicines and medical devices.
• NICE — The National Institute for Health and Care Excellence, which produces evidence-based guidance for health and care in England.
• CQC — The Care Quality Commission, the regulator of health and social care providers in England.
• GMC Specialist Register — The General Medical Council's list of doctors who have completed specialist training in a recognised specialty.
• GPhC — The General Pharmaceutical Council, regulator of pharmacists and registered pharmacies in Great Britain.
• Yellow Card scheme — The MHRA system for reporting suspected side effects of medicines, open to patients as well as clinicians.
• Novel food — The regulatory category covering foods without a significant history of consumption in Great Britain before May 1997, which includes CBD sold as a supplement.

Clinical process and evidence

• Specialist initiation — The rule that only a doctor on the GMC Specialist Register may start a prescription for an unlicensed cannabis-based product.
• Shared care — An arrangement in which a specialist and a GP divide responsibility for a treatment between them.
• Multidisciplinary team (MDT) — A group of clinicians from different disciplines who review a case together.
• Repeat prescription — A further supply issued after the initial prescription, following review.
• Formulary — The list of products a particular clinic or pharmacy is able to prescribe or supply.
• Patient registry — A structured collection of data on patients receiving a treatment outside a clinical trial.
• Real-world evidence — Evidence derived from routine clinical practice rather than from a controlled trial.
• Randomised controlled trial — A study in which participants are randomly assigned to receive a treatment or a comparator, allowing cause and effect to be assessed.
• Placebo — An inactive comparator used in trials, and by extension the improvement people report after receiving one.
• Systematic review — A structured synthesis of all the studies meeting defined criteria on a question, often with a meta-analysis combining their results.
• Patient-reported outcome measure (PROM) — A standardised questionnaire in which patients rate their own symptoms, function or quality of life.
• Contraindication — A circumstance in which a treatment should not be used.
• Drug interaction — An effect one medicine has on how another behaves in the body.
• Adverse event — Any unwanted medical occurrence in someone taking a medicine, whether or not the medicine caused it.
• Red flag — A symptom or sign suggesting a serious underlying cause that needs urgent assessment rather than symptom treatment.

Patient guide · Written by the Flora House editorial team · Last reviewed: 8 September 2026