A stopwatch is a handheld device used to measure time intervals with precision. It typically features a start, stop, and reset button, allowing users to track the duration of events, such as races or cooking times. Stopwatches can be digital or analog, with digital versions often displaying time in hours, minutes, seconds, and fractions of a second. Many athletes and coaches use a stopwatch to improve performance in sports like running or swimming. Some modern smartphones also include a built-in stopwatch function, making it convenient for anyone to time activities without needing a separate device.