A titrant is a solution of known concentration used in a titration process to determine the concentration of an unknown solution. During a titration, the titrant is gradually added to the unknown solution until a chemical reaction reaches its endpoint, which is often indicated by a color change or a specific measurement. Titrants are commonly used in various fields, including chemistry and biology, to analyze substances. For example, in acid-base titrations, a strong acid or strong base can serve as the titrant to find the concentration of an acid or base in a sample.