A crack is a break or fracture in a material, often resulting in a visible separation. This can occur in various substances, such as glass, metal, or concrete, and may be caused by stress, impact, or environmental factors. Cracks can vary in size and depth, affecting the integrity and strength of the material. In construction, cracks in structures like buildings or bridges can indicate potential safety issues. Engineers often assess cracks to determine their cause and severity, deciding whether repairs are necessary to prevent further damage or failure. Regular inspections help maintain the safety and longevity of these structures.