Battle subtypes are always a single word and are listed after a long dash: “Battle — Siege.” Battle subtypes are also called battle types. See rule 205.3q for the complete list of battle types.
July 23, 2021 · Adventures in the Forgotten Realms
Plane subtypes are listed after a long dash, and may be multiple words: “Plane — Serra’s Realm.” All words after the dash are, collectively, a single subtype. Planar subtypes are called planar types. A plane can have only one subtype. See rule 205.3n for the complete list of planar types.