Fatigue life refers to the duration a material or component can withstand repeated loading and unloading cycles before it fails. This concept is crucial in engineering and materials science, as it helps predict when a structure, like a bridge or airplane wing, may develop cracks or fractures due to stress over time. Factors influencing fatigue life include the material's properties, the magnitude of the applied loads, and environmental conditions. Engineers often conduct tests to determine the fatigue life of materials, ensuring safety and reliability in applications involving mechanical components and structural designs.