indicator

1. A pointer or index that indicates something.
2. A meter or gauge.
3. The needle or dial on such a meter.
4. Any of many substances, such as litmus, used to indicate the concentration of a substance, or the degree of a reaction.
5. A plant or animal whose presence is indicative of some specific environment.
6. A measure, such as unemployment rate, which can be used to predict economic trends.
7. A bird, the honeyguide.
8. A codeword that marks the use of a specific cryptic device.

Plural indicators