A litmus test is a simple method used to determine whether a solution is acidic or basic. It involves using litmus paper, which is treated with natural dyes from certain lichens. When the paper is dipped into a solution, it changes color: red for acidic solutions (pH less than 7) and blue for basic solutions (pH greater than 7). In addition to its scientific use, the term "litmus test" is often used metaphorically in various fields, such as politics and ethics, to describe a decisive factor that determines the outcome of a situation or the suitability of a candidate based on specific criteria.