Constitution (CON) in DnD 5e measures a character’s health, stamina, and resilience. It reflects how well a character can endure physical or magical challenges, resist poisons, and sustain strenuous activities.

Key Aspects:

1. Constitution Checks: Unlike other checks, Constitution checks are rare and lack associated skills. They’re usually required when a character tries to surpass their usual physical limits. Situations might include enduring extreme temperatures or resisting a venom’s immediate effects.
2. Hit Points (HP): A character’s Constitution modifier influences their total hit points. When determining hit points for each level, the Constitution modifier is added to the rolled or chosen number. Changes in the modifier can retroactively affect maximum hit points.
3. Classes & Constitution: All characters benefit from a high Constitution due to its influence on HP and resistance to various effects. Front-line fighters like Barbarians or Fighters especially need a strong Constitution to withstand more hits.
4. Constitution Saving Throws: Some classes, including Barbarians, Fighters, and Sorcerers, are proficient in these saving throws.
5. Racial Bonuses: Races such as Dwarves, Stout Halflings, and Half-Orcs have inherent bonuses to Constitution.
6. Role in Gameplay: While no skills are directly tied to Constitution, it’s essential for maintaining HP and resisting the physical or magical strain. For spellcasters, a robust Constitution aids in concentrating on spells under duress.
7. HP Variation by Class: Different classes start with and gain various hit points as they level. For instance, Barbarians generally have the highest HP progression, while Sorcerers and Wizards have the least.