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Glossary
Clinical trial terms, in plain language
Trial listings and consent forms are full of jargon. Here are the words you'll see most often, explained simply — so the next step is clearer.
ClinicalMatchMate helps organize public clinical trial and condition-resource information in plain language. It does not diagnose, recommend treatment, guarantee eligibility, or replace conversations with a clinician or research team.
Last updated: June 4, 2026 · Educational use only
Study phases.
Trials are organized into phases that build on each other. Each phase answers a different question about a treatment.
- Phase 1
- An early study, usually in a small group, focused on safety, dosing, and how the body handles a treatment.
- Phase 2
- A larger study that looks at whether a treatment works for a condition while continuing to watch safety.
- Phase 3
- A larger study comparing the treatment with standard care to confirm benefit and monitor side effects before approval is considered.
- Phase 4
- A study done after a treatment is approved, to track long-term safety and effectiveness in everyday use.
Eligibility & enrollment.
Every study defines who it is studying. These rules keep participants safe and help researchers answer their question. The study team confirms whether a trial is a fit — these terms just describe how that works.
- Eligibility criteria
- The full set of rules that describe who a study is looking for, and who it is not.
- Inclusion criteria
- Requirements someone must meet to be considered for a study (for example, an age range or a specific diagnosis).
- Exclusion criteria
- Factors that may prevent someone from joining a study, often for safety reasons.
- Screening
- The process the study team uses — reviewing history, labs, imaging, and prior treatments — to decide whether a trial is appropriate.
- Enrollment
- Officially joining a study after screening and the informed-consent process are complete.
Study design.
These words describe how a study is set up so its results can be trusted.
- Randomization
- Assigning participants to groups by chance, so the groups are comparable and results are less biased.
- Control group
- A comparison group that may receive standard care or a placebo, used to measure the treatment's effect.
- Placebo
- An inactive substance with no treatment effect, sometimes used for comparison. Not every trial uses one.
- Blinding (masking)
- Keeping participants and/or the study team unaware of group assignments to reduce bias.
- Open-label
- A study in which everyone knows which treatment is being given.
- Endpoint (outcome)
- The specific result a study measures to judge whether a treatment works — for example, a change in a symptom or lab value.
- Protocol
- The detailed plan that describes a study's goals, design, who can take part, and what will happen.
Safety & ethics.
- Informed consent
- An ongoing process — not just a form — where the study team explains the study so a person can decide whether to take part and can leave at any time.
- Adverse event
- Any unwanted medical problem during a study, whether or not it is caused by the treatment.
- Institutional Review Board (IRB)
- An independent committee that reviews a study to help protect the rights and welfare of participants.
- Sponsor
- The organization responsible for starting, managing, or funding a study.
Sources & review.
Written in plain language by ClinicalMatchMate and grounded in public guidance. This page is educational and is not medical advice.
This page is educational and is not medical advice. Trial details can change and should be verified with the trial site or study team. Final eligibility and appropriateness are confirmed only by the study team.