Bottom four-dot fire radical - the side-form of
火 used when fire sits beneath a character. Indexes this char in the heat-and-light family with
热 (hot),
烈 (fierce),
然 (to burn),
煮 (to boil). Carries the 'bright, glowing' image: fire warming and brightening a wide hall, giving the meanings 'bright,' 'genial,' and 'flourishing.'