A stopwatch is typically a handheld gadget, not a feature on a phone or computer. He carried a digital stopwatch during the experiment.
Pro Tip 2/3
Precision Tool
Stopwatches are used when precise timing is crucial, like in sports or scientific experiments. The coach always had a stopwatch at swim meets.
Pro Tip 3/3
Not a Clock
Don't confuse a stopwatch with a clock; it counts durations, not the current time. Her stopwatch showed 9.58 seconds for the sprint, not the time of day.