Tracer

**Semantic type:** Indicator, Reagent, or Diagnostic Aid

**Definition:** A substance that is identifiable by virtue of its radioactive signature, color, or other distinguishing physical property, such as a dye, radioactive isotope, or inert chemical, that is introduced into a biological or mechanical system and can be followed through the course of a process or event.

**Synonyms:** - Label - Labeled - Labeling Agent - Reporter - Tag - Tagged - scan tracer used - scan_tracer_used - tracer