A tuned mass damper is a device used primarily in engineering and architecture to reduce the effects of structural vibrations caused by external forces such as wind, earthquakes, machinery or people walking in unison. It typically consists of a mass attached to a structure via springs and dampers. When the structure vibrates, the mass moves in the opposite direction, counteracting the vibration and reducing the overall movement of the structure. This helps to improve the stability, safety, and comfort of buildings, bridges, and other large structures by minimizing sway and oscillations.