情勢の一変に、政府は対応を迫られた。
Faced with the sudden change in the situation, the government was forced to respond.
彼の態度の一変ぶりに、周囲は驚いた。
Everyone around him was surprised at how completely his attitude had changed.
新しい技術は業界に一変をもたらした。
The new technology brought about a complete transformation of the industry.