Knocking Out a Creature
Source: Player’s Handbook (2024) p. 370. Available in the SRD and the Free Rules (2024)
When you would reduce a creature to 0 Hit Points with a melee attack, you can instead reduce the creature to 1 Hit Point. The creature then has the Unconscious condition and starts a Short Rest.
The creature remains Unconscious until it regains any Hit Points or until someone uses an action to administer first aid to it, which requires a successful DC 10 Wisdom (Medicine) check.