~(아/어)지다 attaches to an adjective to express the sense of changing (said of a quality), like "become" or "turn" in English. For example: - 붉다(red) -> 붉어지다(turn red). - 춥다(cold) -> 추워지다(becomes cold). - 좋다(good) -> 좋아지다(get better). -지다 becomes -졌다 for the past tense, and -질 것이다 for the future. Here are some examples: - 갑자기 날씨가 추워진다 = It's getting cold all of a sudden. - 도박에 빠져서 불행해지는 사람이 많다 = There are many people who ruin their lives because of gambling. - 그 말을 듣고 친구 얼굴이 붉어졌다 = My friend's face turned red hearing that remark. - 겨울이라 날이 빨리 어두워졌다 = As it was winter, the day got dark early. - 내낸엔 경기가 좋아질 것이다 = The economy will get better next year. - 취직했으니까 형편이 좋아질 거야 = You'll be better off now that you've found a job.