A timer is a kind of clock for measuring time intervals. A timer which counts upwards from zero for measuring time is often called a stopwatch. A device which counts down from a specified time interval is more usually called a timer. A simple example is an hourglass. Some timers sound an audible alarm that the time is up. Time switches, timing mechanisms which activate a switch, are sometimes called "timers".
- Robynne Eagan; Tracey Ann Schofield; et al., It's About Time (Carthage, IL: Teaching & Learning Co.,1997), p. 62