Rules glossary
↑ Parent rule: 903.3 Each deck has a legendary card designated as its commander.…
903.3d If an effect refers to controlling a commander, it refers to a permanent on the battlefield that is a commander. If an effect refers to casting a commander, it refers to a spell that is a commander. If an effect refers to a commander in a specific zone, it refers to a card in that zone that is a commander.
No sub-rules.