indicator

noun

• A device providing specific information.
• An instrument that shows temperature, speed etc.
• A species whose presence, absence, or abundance reflects a specific environmental condition
• A substance that changes color to indicate the presence of a particular chemical or condition
• A substance which gives a visible sign, usually by a colour change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution.
• A device providing specific information
• A statistic that provides insight into the performance of an economy
• A gene or DNA sequence with a known location on a chromosome and associated with a particular gene or trait.
• A sign that shows the condition or existence of something