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one line; one stretch (e.g. of road); one strand (e.g. of hair); one beam (e.g. of light); one ray; one length (e.g. of rope)
earnest; resolute; intent; devoted; single-minded
空にひと筋の飛行機雲が伸びていた。
A single contrail stretched across the sky.
彼は研究ひと筋に三十年を捧げてきた。
He has devoted thirty years solely to research.
暗闇の中にひと筋の光が差し込んだ。
A single ray of light shone into the darkness.