Fast Fourier Transform (FFT)–based vibration analysis constitutes a core methodology in the condition monitoring and fault diagnosis of rotating machinery. By converting raw time-domain vibration responses into their corresponding frequency-domain representations, the FFT enables precise identification of fault-related spectral components, including harmonics, sidebands, and characteristic defect frequencies associated with bearings, gears, shafts, and other critical elements. Owing to its computational efficiency, robustness, and compatibility with real-time monitoring systems, FFT analysis has become integral to predictive maintenance strategies across manufacturing, aerospace, automotive, and other industrial sectors. Its application supports early detection of mechanical degradation, enhances operational reliability, and minimizes unplanned equipment downtime through timely intervention.