Indicator - Definition
indicator
n 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 [syn: index,
index number, indicant, indicator]
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