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.