ETYM Latin: cf. French indicateur.
A dial or light that displays information about the status of a device, such as a light connected to a disk drive that glows when the disk is being accessed.
In chemistry, a compound that changes its structure and color in response to its environment. The commonest chemical indicators detect changes in pH (for example, litmus), or in the oxidation state of a system (redox indicators).
1. A device for showing the operating condition of some system.
2. A signal for attracting attention.
An indicator can be defined as something that helps us to understand where we are, where we are going and how far we are from the goal.