Main Entry: in·di·ca·tor

Pronunciation: \ˈin-də-ˌkā-tər\

Function: noun

Date: 1666

1 : one that indicates: as a : an index hand (as on a dial) : pointer b (1) : gauge 2b, dial 4a (2) : an instrument for automatically making a diagram that indicates the pressure in and volume of the working fluid of an engine throughout the cycle
2 a : a substance (as litmus) used to show visually (as by change of color) the condition of a solution with respect to the presence of a particular material (as a free acid or alkali) b : tracer 4b
3 : an organism or ecological community so strictly associated with particular environmental conditions that its presence is indicative of the existence of these conditions
4 : any of a group of statistical values (as level of employment) that taken together give an indication of the health of the economy

— in·dic·a·to·ry \in-ˈdi-kə-ˌtȯr-ē\ adjective