This document defines safety signs and their purposes. It discusses the four basic categories of safety signs - prohibition signs, mandatory signs, warning signs, and information signs. Each category is defined by its shape, color, and meaning. Prohibition signs are circular and red, indicating an action that must not be done. Mandatory signs are circular and blue, showing an action that must be done. Warning signs are triangular and yellow, warning of hazards or dangers. Information signs are square or rectangular and green, providing safety-related information. Examples of common signs from each category are provided.