Bloodied Condition

A creature becomes bloodied when they are reduced to half their maximum hit points or lower. The aarakocra in the Monster Manual has 13 (3d8) hit points. Its hit point maximum is 13 and its bloodied value, half of its maximum, is 6 hit points.

When a creature becomes bloodied, this should be expressed to the players. If a dragon is struck by a mighty blow from an axe, you might describe the attack as "Your axe swings out battering into the dragon and breaking through scales. The dragon is breathing heavily as it bleeds from many wounds. It is bloodied." This gives the player an idea of how their enemies and allies are looking in battle in a non-meta way.