• 木炭もくたん — wood charcoal
• 炭火すみび — charcoal fire
• 炭素たんそ — carbon
• 炭酸たんさん — carbonic acid / soda
• 活性炭かっせいたん — activated charcoal
• 炭鉱たんこう — coal mine
• 炭化たんか — carbonization
• 炭水化物たんすいかぶつ — carbohydrate

炭 combines the radical 火 (fire) with a phonetic element suggesting “black” or “burned.” It appears in both traditional uses like charcoal for fuel and modern terms such as carbon and carbon dioxide.