What does the term "power reserve" refer to in mechanical watches?

The term "power reserve" in mechanical watches specifically refers to the amount of time that a watch will continue to run after it has been fully wound. In a mechanical watch, energy is stored when the mainspring is wound, and this energy is released gradually to keep the watch running. The power reserve indicates how long the watch can operate on that accumulated energy before it stops, which can vary depending on the watch's design and the capacity of its mainspring.

Understanding power reserve is crucial for both watch enthusiasts and collectors, as it helps in determining the practicality of wearing the watch regularly or needing to wind it frequently. A longer power reserve means that the watch can run for a more extended period without requiring additional winding. This characteristic is especially significant for automatic watches, where the power reserve allows for continued operation even when not worn daily.