litmus

/ˈlɪtməs/
noun
  1. A test or indicator that reveals the true nature or status of something.
    • The election results were a litmus test for the popularity of the new policy.
    • Her reaction to the news served as a litmus for her true feelings.
    • Customer satisfaction is often used as a litmus for business success.
  2. A dye obtained from lichens that changes color in acid or base solutions, used as a chemical indicator.
    • The chemistry teacher used litmus paper to test whether the liquid was an acid or a base.
    • Litmus turns red in acidic solutions and blue in alkaline ones.
    • They dipped a strip of litmus into the beaker to check the pH level.
What does "litmus" mean? | whatsthatwordmean | whatsthatwordmean