Meaning & Definition of Indicator in English

1. A number or ratio (a value on a scale of measurement) derived from a series of observed facts

• Can reveal relative changes as a function of time

2. A signal for attracting attention

3. A device for showing the operating condition of some system

4. (chemistry) a substance that changes color to indicate the presence of some ion or substance

• Can be used to indicate the completion of a chemical reaction or (in medicine) to test for a particular reaction