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Constitution represents your character's health and stamina. A Constitution bonus increases a character's hit points, so the ability is important for all classes. Some creatures, such as undead and constructs, do not have a Constitution score. Their modifier is +0 for any Constitution-based checks. A character with a Constitution score of 0 is dead.
You apply your character's Constitution modifier to:
- Each roll of a Hit Die (though a penalty can never drop a result below 1—that is, a character always gains at least 1 hit point each time he advances in level).
- Fortitude saving throws, for resisting poison, disease, and similar threats.
If a character's Constitution score changes enough to alter his or her Constitution modifier, the character's hit points also increase or decrease accordingly.