VITAMINS & SUPPLEMENTS · GUIDE
Nootropics Glossary: Terms From Acetylcholine to Racetam
Plain-language definitions of terms used in brain-supplement and nootropic discussions, from acetylcholine to racetam, with links to the pages that explain each one in depth.
Content last updated . This page has not been medically reviewed.
Back to NootropicsThis glossary explains words you will meet when reading about brain supplements, "smart drugs" and memory products. It is information only. It is not advice about what to take, and it does not replace a clinician or pharmacist. Definitions come from the official sources named in each row. Where the sources we read do not define a term, the row says so and points to the page on this site that covers it. For an overview of the whole library, start at the Nootropics hub.
How to read the table
Entries run roughly A to Z. "Read more" links go to the page on this site that owns the topic. A term appearing here does not mean the ingredient works, is legal everywhere, or is safe for you.Terms A to C
| Term | Plain meaning | Read more |
|---|---|---|
| ADHD | Attention-deficit/hyperactivity disorder. NIMH calls it a neurodevelopmental disorder marked by inattention, hyperactivity and impulsivity. [1] NCCIH says research on carnitine and several herbs, including ginkgo, has not shown that they improve ADHD symptoms. [2] | More about ADHD → |
| Acetylcholine | A chemical messenger in the nervous system. A 2026 review describes its "conventional role as a neurotransmitter". [3] Products marketed around it are covered on the choline pages. | More about Acetylcholine → |
| Adaptogen | A herb group name used in marketing and traditional-medicine writing. The sources we read for this glossary do not define it, so this site compares it with "nootropic" on its own page. | More about Adaptogen → |
| Adverse event | A bad reaction or side effect. FDA asks people to stop the product, seek medical care and report it. [4] | More about Adverse event → |
| Alpha-GPC and citicoline | Choline-related ingredients sold for memory. This page does not assess them; the library does. | More about Alpha-GPC and citicoline → |
| Blood-brain barrier | A specialized structure that regulates what passes between the blood and the central nervous system. [5] FDA says picamilon crosses it, but that is a statement about that ingredient only. [6] | More about Blood-brain barrier → |
| Brain fog | A common phrase for muddled thinking. The sources we read for this glossary do not give a medical definition. | More about Brain fog → |
| Caffeine | MedlinePlus: a bitter substance found naturally in more than 60 plants, and also made synthetically for medicines, foods and drinks. [7] It stimulates the central nervous system. [8] | More about Caffeine → |
| Caffeine withdrawal | MedlinePlus lists headaches, drowsiness, irritability, nausea and trouble concentrating after regular use stops suddenly, usually clearing in a couple of days. [7] | More about Caffeine withdrawal → |
| Cognition, cognitive health | NIA: the ability to think, learn and remember clearly. [9] | More about Cognition, cognitive health → |
Terms D to M
| Term | Plain meaning | Read more |
|---|---|---|
| Dementia | NIA: loss of thinking, remembering and reasoning to the point that it interferes with daily life. [10] | More about Dementia → |
| Dietary supplement | FDA: products intended to add to the diet, in forms such as tablets, capsules, powders, gummies and liquids. [4] If a product is intended to treat or prevent disease, FDA says it is generally a drug, even if labeled as a supplement. [4] | More about Dietary supplement → |
| Drug interaction | When one substance changes how another acts. FDA notes some supplements can interact with medications. [4] | More about Drug interaction → |
| Extract, "standardized" | NCCIH says a maker's use of "standardized", "verified" or "certified" does not necessarily guarantee quality or consistency. [11] | More about Extract, "standardized" → |
| Health claim | FDA: a statement linking a food substance to reduced risk of a disease or health-related condition. [12] | More about Health claim → |
| Hidden ingredient | FDA: an ingredient not listed on the label, often a prescription drug ingredient or banned substance. [13] | More about Hidden ingredient → |
| Mild cognitive impairment (MCI) | NIA: more memory or thinking problems than other adults the same age. [14] | More about Mild cognitive impairment (MCI) → |
| Modafinil | MedlinePlus: a prescription wakefulness-promoting medicine for sleepiness from narcolepsy, shift work sleep disorder or obstructive sleep apnea. [15] | More about Modafinil → |
Terms N to Z
| Term | Plain meaning | Read more |
|---|---|---|
| Neurotransmitter | A chemical messenger between nerve cells; acetylcholine is one example. [3] Marketing that names neurotransmitters is checked on the science pages. | More about Neurotransmitter → |
| Nootropic | UK regulator MHRA used "smart drugs, also known as cognitive enhancers or nootropics" in a 2014 statement. [16] FDA notes some unapproved products are marketed as a "nootropic" cognitive enhancer. [17] It is a marketing and popular term, not a category the sources we read define. | More about Nootropic → |
| Phenibut | FDA (2023): does not meet the legal definition of a dietary ingredient, so supplements declaring it are misbranded. [18] | More about Phenibut → |
| Picamilon | FDA: a chemical made from niacin and GABA; used as a prescription drug in Russia and not approved as a drug in the US. [6] | More about Picamilon → |
| Placebo | NCCIH: an inactive substance that looks like the treatment being tested. [19] | More about Placebo → |
| Prescription stimulant | NIDA says stimulants are most often prescribed for ADHD and are among the most commonly misused prescription drugs. [20] | More about Prescription stimulant → |
| Proprietary blend, stack | Marketing terms. The sources we read for this glossary do not define them; the library pages do. | More about Proprietary blend, stack → |
| Pure caffeine powder | FDA: pure and highly concentrated caffeine products are a significant public health threat and have contributed to at least two US deaths. [21] | More about Pure caffeine powder → |
| Racetam | A family of drug-like compounds. MHRA's 2014 seizure list included several racetams such as phenylpiracetam and aniracetam, and said selling prescription-only or unlicensed medicine is an offence in the UK. [16] | More about Racetam → |
| Randomized controlled trial | NCCIH: volunteers are randomly assigned to a test group or a placebo group. [19] | More about Randomized controlled trial → |
| Serotonin syndrome | MedlinePlus: a potentially life-threatening reaction in which the body has too much serotonin. [22] | More about Serotonin syndrome → |
| Smart drug | Popular term; MHRA treats it as a synonym of cognitive enhancer and nootropic. [16] | More about Smart drug → |
| Structure/function claim | NCCIH: describes an effect on the body's normal structure or function and must carry an FDA disclaimer. [11] | More about Structure/function claim → |
| Tianeptine | FDA (2025): not approved for any medical use in the US, yet marketed as a "nootropic". [17] | More about Tianeptine → |
| Tolerance, dependence | MedlinePlus lists "dependency, so you need to take more" among caffeine's possible problems. [7] | More about Tolerance, dependence → |
| Vinpocetine | FDA: synthetic compound; in 2019 FDA advised pregnant women and those who could become pregnant not to take it. [23] | More about Vinpocetine → |
Words that are easy to misread
"Natural" does not mean safe: FDA advises not to assume it does. [4] "Studied" does not mean "works": for example, NCCIH says there is no conclusive evidence that ginkgo is efficacious in preventing or slowing dementia or cognitive decline. [24] NIA says no vitamin or supplement is recommended for preventing Alzheimer's or other forms of cognitive decline. [9]Frequently asked questions
Is "nootropic" an official term?
The sources we read do not define it as a regulatory category. MHRA used it alongside "smart drugs" and "cognitive enhancers" in 2014, [16] and FDA notes unapproved products being marketed as a "nootropic". [17] See what are nootropics.
Does a term appearing in this glossary mean the ingredient is approved?
No. Phenibut, tianeptine and picamilon are defined here because they are sold or discussed, and FDA states they do not meet the dietary ingredient definition or are not approved for medical use. [18] [17] [6]
What is the difference between a supplement and a drug?
FDA says a product intended to treat, diagnose, cure or prevent disease is generally a drug even if labeled a supplement. [4] Prescription medicines such as modafinil are used under clinician direction. [15]
Where can I check an interaction with my medicines?
Ask a pharmacist or clinician, and read medication interactions. NCCIH advises telling health providers about all supplements you use. [11]
Where do I report a problem with a product?
FDA asks people to stop the product, seek care and file a report through its Safety Reporting Portal. [25] See side effects and reporting.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety reminder
Supplements can interact with medicines, affect surgery and anesthesia, and have not been tested in pregnant women, nursing mothers or children for many products. [11] Ask a clinician or pharmacist before starting anything, see the safety quick reference, and in the US call Poison Help at 1-800-222-1222 for poisoning questions or 911 in an emergency. [8]
References
- National Institute of Mental Health (NIMH), Attention-Deficit/Hyperactivity Disorder. Read 2026-10-23.
- NCCIH, Attention-Deficit Hyperactivity Disorder at a Glance. Read 2026-10-23.
- Scoping review on acetylcholine, PubMed 42817194, 2026. Abstract read 2026-10-23.
- FDA, FDA 101: Dietary Supplements. Read 2026-10-23.
- Review article on the blood-brain barrier, PubMed 42904547, 2026. Abstract read 2026-10-23.
- FDA, Picamilon in Dietary Supplements. Read 2026-10-23.
- MedlinePlus (U.S. National Library of Medicine), Caffeine. Read 2026-10-23.
- MedlinePlus Medical Encyclopedia, Caffeine overdose. Read 2026-10-23.
- National Institute on Aging (NIA), Cognitive Health and Older Adults. Read 2026-10-23.
- NIA, What Is Dementia? Symptoms, Types, and Diagnosis. Read 2026-10-23.
- National Center for Complementary and Integrative Health (NCCIH), Using Dietary Supplements Wisely. Read 2026-10-23.
- FDA, Label Claims for Conventional Foods and Dietary Supplements. Read 2026-10-23.
- FDA, Avoiding Products Contaminated with Hidden Ingredients. Read 2026-10-23.
- NIA, What Is Mild Cognitive Impairment?. Read 2026-10-23.
- MedlinePlus Drug Information, Modafinil. Read 2026-10-23.
- UK Medicines and Healthcare products Regulatory Agency (MHRA), Medicines watchdog makes record seizure of experimental smart drugs, 24 October 2014. Read 2026-10-23.
- FDA, FDA warns consumers not to purchase or use any tianeptine product due to serious risks, updated 05/08/2025. Read 2026-10-23.
- FDA, Phenibut in Dietary Supplements, content current as of 07/12/2023. Read 2026-10-23.
- NCCIH, Placebo Effect, last updated January 2020. Read 2026-10-23.
- National Institute on Drug Abuse (NIDA), Misuse of Prescription Drugs Research Report: Overview, 6 March 2026 (reached from the prescription stimulants DrugFacts page). Read 2026-10-23.
- FDA, Pure and Highly Concentrated Caffeine, content current as of 03/06/2023. Read 2026-10-23.
- MedlinePlus Medical Encyclopedia, Serotonin syndrome. Read 2026-10-23.
- FDA, Vinpocetine in Dietary Supplements. Read 2026-10-23.
- NCCIH Clinical Digest, Dietary Supplements and Cognitive Function, Dementia, and Alzheimer's Disease: What the Science Says, July 2022. Read 2026-10-23.
- FDA, How to Report a Problem with Dietary Supplements, content current as of 03/13/2025. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.