indicator indicator /ˈɪndəˌkeɪtɝ/

noun

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  ( index number , indicant , index , indicator )
   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
     The rising temperature was an indicator of the approaching storm.
   The rising temperature was an indicator of the approaching storm.
   
2. () A device for showing the operating condition of some system  ( indicator )
   a device for showing the operating condition of some system
    Make sure to use your indicator when you're changing lanes on the highway
   Make sure to use your indicator when you're changing lanes on the highway
   
   
3. () A signal for attracting attention  ( indicator )
   a signal for attracting attention
   
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  ( indicator )
   (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