A stopwatch is a handheld device used to measure time intervals with high precision. It typically features a start, stop, and reset button, allowing users to track the duration of events or activities. Stopwatches are commonly used in sports, laboratories, and various timed activities. Modern stopwatches can be digital or analog, with digital versions often displaying time in hours, minutes, seconds, and fractions of a second. Some advanced models may include additional features like lap timing, memory functions, and synchronization with other devices, making them versatile tools for timing needs.