Knocking Creatures Unconscious
When you reduce a creature to 0 hit points or fewer, you can choose to knock it unconscious rather than kill it. Until it regains hit points, the creature is unconscious but not dying. Any healing makes the creature conscious. If the creature doesn’t receive any healing, it is restored to 1 hit point and becomes conscious after a short rest.
Published in Player's Handbook, page(s) 295.