Litmus

Definitions

1. A dyestuff extracted from certain lichens, that changes color when exposed to pH levels greater than or less than certain critical levels.
   uncountable
2. A simple test of acidity in a liquid using litmus, usually in the form of litmus paper.
   countable, uncountable
3. A simple test of any attribute; a litmus test.
   countable, uncountable

Equivalents

CEFR level