Left-side fire radical — pictograph of flames rising in three tongues (the simplified standalone
火, distinct from the four-dot bottom-fire
灬). The indexing radical, naturally so:
炽 means blazing-hot, fiercely burning (
炽热 white-hot,
炽烈 fierce-intense). Used figuratively for any intense passion or activity. Same fire-family:
焰 flame,
烧 to burn,
烫 scalding,
燃 to ignite,
灼 to scorch.