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to become red; to redden; to blush
褒められて彼女の頬がうっすらと赧らんだ。
When she was praised, her cheeks faintly reddened.
寒さで鼻の頭が赧らんでいるのに気づいた。
I noticed the tip of my nose had reddened from the cold.
紅葉が進んで山全体が赧らんで見えた。
As autumn progressed, the entire mountain appeared to have turned red.