people in general (often used in the plural); "they're just country folk"; "folks around here drink moonshine"; "the common people determine the group character and preserve its customs from one generation to the next"
a device for showing the operating condition of some system
a signal for attracting attention
(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