A stopwatch is a type of timer device designed to measure the amount of time elapsed, from a start point when it is activated to the time when it is deactivated. Stopwatches are used in a wide range of applications from sporting events to experiments and provide a precise time measurement from start to finish. Stopwatches are available in digital and analogue format; digital stopwatches are battery powered and analogue watches are mechanical. There are also differences in resolution between the two; analogue stopwatches provide a resolution or accuracy of 1/5 s and digital watches in most of the cases deliver 1/100 s.
A timer or desktop timer is a device used to measure down from a set time. Timers are programmable and have an interface with buttons including start, stop, reset and mode. Timers usually have digital display with an LCD screen. Analogue timers are mechanical and have a dial that you twist round to the countdown time you require. Both digital and analogue timers feature an alarm that goes off when the countdown time is reached.