Glossary of Common Site Terms

This glossary will help you understand words and phrases frequently used on ClinicalTrials.gov. Many of these words are also used by clinical researchers and others in the same or a similar manner. But the definitions below are provided to explain content on ClinicalTrials.gov only.

Accepts Healthy Volunteers

A type of eligibility criteria that indicates whether people who do not have the condition/disease being studied can participate in that clinical study.

Active Comparator arm

An arm type in which a group of participants receives an intervention/treatment considered to be effective (or active) by health care providers.

Adverse Event

An unfavorable change in the health of a participant, including abnormal laboratory findings, that happens during a clinical study or within a certain amount of time after the study has ended. This change may or may not be caused by the intervention/treatment being studied.


More on Clinical Trial Education:

Clinical Trials: Benefits, Risks, and Safetyexternal link, opens in a new tab
Learn About Clinical Studiesexternal link, opens in a new tab
Finding a Clinical Trialexternal link, opens in a new tab