a positive feeling of liking; "he had trouble expressing the affection he felt"; "the child won everyone's heart"; "the warmness of his welcome made us feel right at home"
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