What Is a DOI?
A DOI is a permanent digital identifier for a published item that links to its web location. Learn how to read one and why it does not prove quality.
1 min readResearch Glossary
Short plain-English definitions of common research and publishing terms, with links to deeper guides.
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What Is a PMID?
A PMID is the unique number PubMed assigns to each citation record. See what it identifies, how to find it and why it is not a quality mark.
1 min readWhat Is a PMCID?
A PMCID is the identifier PubMed Central assigns to a full-text article in its archive. Learn how it differs from a PMID and how to use it.
1 min readWhat Is ORCID?
ORCID is a free, persistent identifier for researchers that links you to your works and avoids name confusion. See what it is and what it is not.
1 min readWhat Is an ISSN?
An ISSN is an eight-digit number that identifies a serial publication such as a journal. Learn what it identifies and why it is not a quality signal.
1 min readWhat Is a Preprint?
A preprint is a research paper shared publicly before peer review. Learn how preprints work, how to cite them and why to treat them with caution.
1 min readWhat Is a Research Protocol?
A research protocol is the written plan for a study: its question, methods and analysis. Learn what it contains and why changes must be documented.
1 min readWhat Is a Research Hypothesis?
A research hypothesis is a testable prediction about the relationship between variables. See what makes one testable and how it differs from an aim.
1 min readWhat Is a Primary Outcome?
The primary outcome is the main result a study is designed to measure, used to plan the sample size and judge success. Learn how to define one.
1 min readWhat Is a Secondary Outcome?
A secondary outcome is an additional measure a study reports alongside its primary outcome. Learn how to interpret secondary outcomes cautiously.
1 min readWhat Is a Confounder?
A confounder is a third factor linked to both exposure and outcome that distorts their apparent relationship. See an example and how to handle it.
1 min readWhat Is a Control Group?
A control group is the comparison group in a study that does not receive the intervention being tested. Learn the types and why comparison matters.
1 min readWhat Is Randomization?
Randomization assigns participants to study groups by chance to reduce bias. Learn how it works, common methods and why it is not the same as random sampling.
1 min readWhat Is Blinding?
Blinding (masking) hides group assignment from participants, clinicians or assessors to reduce bias. See who can be blinded and why it is not always possible.
1 min readWhat Is Allocation Concealment?
Allocation concealment hides the upcoming assignment from those enrolling participants in a trial. Learn how it differs from blinding and why it matters.
1 min readWhat Is a Forest Plot?
A forest plot displays each study's effect with its confidence interval and a pooled result in a meta-analysis. Learn how to read the symbols.
1 min readWhat Is a Funnel Plot?
A funnel plot graphs study effects against precision to check for small-study effects such as publication bias. Learn how to read one cautiously.
1 min readWhat Is Heterogeneity?
Heterogeneity is variation in results between studies beyond chance. Learn the main types and how it is detected in meta-analysis.
1 min readWhat Is Meta-Regression?
Meta-regression examines whether study-level characteristics explain differences in effects between studies. Learn its purpose and limits.
1 min readWhat Is a PRISMA Flow Diagram?
A PRISMA flow diagram shows how records move through a systematic review, from identification to inclusion. Learn what its boxes report.
1 min readWhat Is PROSPERO?
PROSPERO is an international register of systematic review protocols that records review plans before they start. Learn who runs it and what it does.
1 min readWhat Is the GRADE Framework?
The GRADE framework rates how certain we can be about estimated effects as high, moderate, low or very low. Learn the main factors it considers.
1 min readWhat Is a Reporting Guideline?
A reporting guideline is a checklist of what to include when writing up a study. Learn what they are and how to find the one for your design.
1 min readWhat Is a CONSORT Checklist?
The CONSORT checklist is a reporting guideline for randomised trials. Learn what it covers and how it helps readers judge a trial.
1 min readWhat Is a STROBE Checklist?
The STROBE checklist is a reporting guideline for observational studies (cohort, case-control, cross-sectional). Learn what it covers.
1 min readWhat Is the CARE Checklist?
The CARE checklist is a reporting guideline for case reports. Learn what it covers and where to download the official version.
1 min readWhat Is an Embargo in Academic Publishing?
An embargo in academic publishing is a restriction on when information or a full text may be shared publicly. Learn the main kinds.
1 min readWhat Is an Erratum?
An erratum is a notice published by a journal to correct an error in an article. Learn when errata are used and how they differ from retractions.
1 min readWhat Is a Retraction?
A retraction is a formal notice that a published article is withdrawn because its findings or conduct are unreliable. Learn reasons and how to cite retracted work.
1 min readWhat Is an Expression of Concern?
An expression of concern is an editor's notice that a published article may be unreliable while an investigation is ongoing. Learn how it differs from a retraction.
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