"Schedule I" refers to a classification under the Controlled Substances Act in the United States. It designates drugs and substances that are considered to have a high potential for abuse, no accepted medical use, and a lack of accepted safety for use under medical supervision. Examples include heroin and LSD. Substances classified as Schedule I are subject to strict regulations and are illegal to manufacture, distribute, or possess. This classification aims to control the use of these substances due to their potential for addiction and harm, impacting public health and safety.