-았/었다가 — Did ... and then, Did ... but then

This expression indicates that the subject performs the action in the following clause after the action in the first clause is completed. Note that in this case the -았/었- part of ‘-았/었다가’ does not indicate the past tense but rather the completion of the action. As for the following clause, all tenses can be used, including the past, present, and future. The phrase -았/었다가 can also be shortened to -았/었다. Finally, this expression can only be attached to verbs.

Details

1. The subjects of the preceding and following clauses must be the same.

양강 씨는 편지를 썼다가 자야 씨가 찢었어요. ✕

2. In general, the actions described by the preceding and following clauses reflect mutually contrastive or opposite situations.

코트를 입었다가 벗었어요.

I put on the coat and then took it off.

불을 껐다가 어두워서 다시 켰어요.

I turned the lights off but then turned them back on because it was dark.

일어났다가 졸려서 다시 잤어요.

I woke up but then went back to sleep because I was sleepy.

3. This expression can also be used to indicate the speaker’s doing of some action and then experiencing something noteworthy or unexpected while doing that action. In this case, it usually refers to the occurrence of an unplanned event after doing the action in the preceding clause, it is mainly used to refer to past events and is used together with verbs such as 가다, 오다, 타다 and 들르다. When used in this meaning, it can be replaced with the expression -았/었는데 with no change in meaning.

백화점에 갔다가 우연히 고등학교 때 친구를 만났어요.

I went to the department store and happened to bump into a high school friend.

서점에 들렀다가 재미있는 책을 발견했어요.

I went by the bookstore and came across an interesting book.

While -다가 and -았/었다가 are two similar forms, they have a number of differences as shown below.