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flame; blaze
flames (of intense emotion, e.g. love, jealousy, anger); passion
「炎」 has another reading with different meanings.
ろうそくの炎を見つめて考え事をした。
I gazed at the candle flame, lost in thought.
ろうそくの炎が揺れている。
The candle flame is flickering.
炎が建物全体に広がるまでわずか数分だった。
It took only a few minutes for the flames to spread across the entire building.