a turning point; the moment or occasion when a situation or someone's life begins to change significantly.
彼の病気が治ったことが、人生の転機になった。
His recovery from illness became a turning point in his life.
その事故は会社にとって経営方針を見直す転機となった。
That accident became a turning point prompting the company to review its management policy.
留学は私にとって価値観が変わる大きな転機だった。
Studying abroad was a major turning point that changed my values.