An Active Pharmaceutical Ingredient (API) is the substance in a medication that produces the intended therapeutic effect. It is the key component responsible for the drug's effectiveness in treating a specific condition or disease. APIs can be derived from natural sources or synthesized through chemical processes. In the pharmaceutical industry, the quality and purity of APIs are crucial for ensuring patient safety and drug efficacy. Regulatory agencies, such as the U.S. Food and Drug Administration (FDA), set strict guidelines for the manufacturing and testing of APIs to maintain high standards in drug development and production.