Core:Short Rest

A short rest is a period of downtime, at least 1 hour long, during which a creature does nothing more strenuous than eating, drinking, reading, and tending to wounds.

A creature can spend one or more hit dice at the end of a short rest, up to the creature's total number of hit dice. For each hit die spent in this way, the creature regains that many HP + P. A creature regains some spent hit dice when it finishes a long rest.