燃焼
ねんしょう · nenshou · JLPT N1 · noun
combustion
🔥 燃 burn + 焼 burn/bake = double burn, so 燃焼 means burning or combustion
Both characters share the idea of burning. 燃 (moeru) means to catch fire, and 焼 (yaku) means to scorch or bake. Together they name the process of burning.