Ability Damaged: The character has temporarily lost 1 or more ability score points. If an attack that causes ability damage scores a critical hit, it drains twice the indicated amount (if the damage is expressed as a die range, roll two dice). Lost points return at a rate of 1 per day unless noted otherwise by the condition dealing the damage. A character with Strength 0 falls to the ground and is helpless. A character with Dexterity 0 is paralyzed. A character with Constitution 0 is dead. A character with Intelligence, Wisdom, or Charisma 0 is unconscious.
Ability damage is different from penalties to ability scores, which go away when the conditions causing them (fatigue, entanglement, and so on) go away.
Ability Score Loss
While any loss is debilitating, losing all points in an ability score can be devastating.
* Strength 0 means that the character cannot move at all. He lies helpless on the ground.
* Dexterity 0 means that the character cannot move at all. He stands motionless, rigid, and helpless.
* Constitution 0 means that the character is dead.
* Intelligence 0 means that the character cannot think and is unconscious in a coma-like stupor, helpless.
* Wisdom 0 means that the character is withdrawn into a deep sleep filled with nightmares, helpless.
* Charisma 0 means that the character is withdrawn into a catatonic, coma-like stupor, helpless.
Keeping track of negative ability score points is never necessary. A character’s ability score can’t drop below 0.
Having a score of 0 in an ability is different from having no ability score whatsoever.
Some spells or abilities impose an effective ability score reduction, which is different from ability score loss. Any such reduction disappears at the end of the spell’s or ability’s duration, and the ability score immediately returns to its former value.
If a character’s Constitution score drops, then he loses 1 hit point per Hit Die for every point by which his Constitution modifier drops. A hit point score can’t be reduced by Constitution damage or drain to less than 1 hit point per Hit Die.