Research Library Glossary
Plain definitions of research terms used in the Research Library, from meta-analysis and placebo to biomarker, pharmacokinetics and phenotype, with what each can and cannot show.
Content last updated . This page has not been medically reviewed.
How to use this glossary
These are short, plain definitions of terms you will meet in study records and guides. A definition tells you what a word means. It does not tell you whether any herb or ingredient works. Terms are grouped by topic.Study types and methods
| Term | Plain meaning | What it can and cannot show |
|---|---|---|
| Clinical trial | A study done in people, following a written plan called a protocol [1] | Can compare approaches; a registered trial is only a plan until results exist |
| Randomized controlled trial | Volunteers are randomly assigned to a test group or a control group [2] | Comparing groups suggests whether changes come from the treatment or from chance; design quality still varies |
| Control group | The comparison group, given a standard treatment or a placebo [3] | Needed to judge an effect; it is not a treatment itself |
| Placebo | An inactive substance that looks like the treatment being tested [2] | Helps separate a treatment's effect from expectation |
| Placebo effect | A beneficial outcome that comes from a person's anticipation that an intervention will help [2] | Real as an experience; not evidence that the tested substance works |
| Blinding | Nobody knows who has been given which treatment [3] | Reduces bias in comparing outcomes |
| Trial phase | A stage of testing, from small early Phase 1 studies to large Phase 3 studies [1] | Shows stage, not quality or success; the library records a phase for about two thirds of trials |
Combining research
| Term | Plain meaning | What it can and cannot show |
|---|---|---|
| Systematic review | A review that tries to find and weigh all the research meeting pre-set eligibility criteria on one question, using methods meant to reduce bias [4] | Only as good as the studies it finds; a review registration is not a finished review |
| Meta-analysis | Results of individual studies are combined into one overall statistic [4] | Can give a more precise estimate; not every review includes one, for example when the studies are too different [4] |
| PRISMA | A guideline for how to report a systematic review: why it was done, what methods were used, what was found [5] | Shows reporting, not that the conclusions are right |
| Abstract | A short summary of a paper; PubMed holds citations and abstracts, not full articles [6] | Quick orientation only; read the paper for details |
Laboratory and body processes
| Term | Plain meaning | What it can and cannot show |
|---|---|---|
| Preclinical research | Work done before testing in people; the two types are in vitro (laboratory) and in vivo (in living animals) [7] | Looks for potential harm; animal and cell research is not human evidence |
| Pharmacokinetics | What the body does to a substance: how it is absorbed, distributed, metabolized and excreted [8] | Explains how much reaches the body and for how long; it does not show a health outcome |
| Biomarker | A defined characteristic measured as an indicator of normal processes, disease processes, or responses to an exposure or intervention [9] | Not an assessment of how a person feels, functions or survives, so a change in a biomarker is not a health result [9] |
Genes, traits and vocabularies
| Term | Plain meaning | What it can and cannot show |
|---|---|---|
| Gene | The basic unit of inheritance, made of DNA; many genes carry instructions to make proteins [10] | A gene record names a unit; it does not describe a health effect by itself |
| Gene symbol | A short combination of letters and sometimes numbers that abbreviates a gene's name [10] | A label for finding the gene |
| Phenotype | An individual's observable traits, shaped by genes and environment [11] | Library phenotype terms are vocabulary entries, not diagnoses |
| Ontology | A controlled, standardized vocabulary describing things and the relationships between them [12] | Helps records line up; it does not check the facts behind them |
Plants and products
| Term | Plain meaning | What it can and cannot show |
|---|---|---|
| Herb | A plant or plant part used for scent, flavor or therapeutic properties [13] | A name; it does not say how the plant was prepared or tested |
| Dietary supplement | Under federal law, a product taken by mouth, made to supplement the diet and labeled as a supplement, which can include herbs or other botanicals [14] | Products can differ from those tested in studies [14] |
| Complementary | A non-mainstream approach used together with conventional medicine [15] | A way of describing use, not evidence of effect |
| Alternative | A non-mainstream approach used in place of conventional medicine [15] | Same: describes use, not effect |
Terms specific to the library
- Imported record: a record brought in from a public database or ontology. None has been reviewed by a clinician.
- Study record: one of three types: a registered clinical trial, a systematic-review registration, or a publication record with a PubMed ID and abstract.
- Name match: a connection found by matching text. It can be wrong.
- Research model: a label of human, animal or cell research taken from the source data.
Related pages
For how these terms appear on records, see How to Read Research Library Records. Study design is explained further in Evidence Types and Study Designs, and the difference between animal and human work in Human, Animal and Laboratory Research.Frequently asked questions
What is a meta-analysis?
It combines the results of individual studies into one overall statistic, which may give a more precise estimate. [4] Not every systematic review has one.
What is a placebo?
An inactive substance that looks like the treatment being tested. [2] It lets researchers compare a real treatment against expectation.
What is a biomarker?
A measured characteristic that indicates a normal process, a disease process or a response to an exposure or intervention. [9] A biomarker is not an assessment of how someone feels, functions or survives.
What is pharmacokinetics?
It is the study of how a substance is absorbed, distributed, metabolized and excreted by the body. [8]
What is a systematic review?
A review that tries to identify, appraise and combine all the evidence meeting pre-specified criteria for a research question, using methods meant to reduce bias. [4]
References
- FDA, The Drug Development Process, Step 3: Clinical Research. Step 3: Clinical Research. Read 2026-10-22.
- NCCIH, Placebo Effect. Placebo Effect. Read 2026-10-22.
- NHS, Clinical trials. Clinical trials. Read 2026-10-22.
- Cochrane Library, About Cochrane Reviews. About Cochrane Reviews. Read 2026-10-22.
- PRISMA statement website. PRISMA statement. Read 2026-10-22.
- National Library of Medicine, About PubMed. About PubMed. Read 2026-10-22.
- FDA, The Drug Development Process, Step 2: Preclinical Research. Step 2: Preclinical Research. Read 2026-10-22.
- FDA, The Drug Development Process, Step 1: Discovery and Development. Step 1: Discovery and Development. Read 2026-10-22.
- FDA, Biomarker Qualification Program, About Biomarkers and Qualification. About Biomarkers and Qualification. Read 2026-10-22.
- MedlinePlus Genetics, What is a gene?. What is a gene?. Read 2026-10-22.
- NHGRI, Talking Glossary of Genomic and Genetic Terms: Phenotype. Phenotype. Read 2026-10-22.
- Human Phenotype Ontology, About. About the Human Phenotype Ontology. Read 2026-10-22.
- MedlinePlus, Herbal Medicine. Herbal Medicine. Read 2026-10-22.
- NCCIH, Using Dietary Supplements Wisely. Using Dietary Supplements Wisely. Read 2026-10-22.
- NCCIH, Complementary, Alternative, or Integrative Health: What’s In a Name?. Complementary, Alternative, or Integrative Health: What’s In a Name?. Read 2026-10-22.
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.