Learn to say when something happens using -(으)ㄹ 때, and use -았/었을 때 for something that was already finished.
By the end, you can attach -(으)ㄹ 때 to verbs and adjectives, including ㄹ-stems and ㅂ-adjectives, to say when something happens. You can also choose between 갈 때 and 갔을 때 correctly.
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