The PURPOSIVE form -(으)러 is used to express going or coming for the purpose of… This pattern is typically used with verbs of motion like 가- and 오-. The ending is attached straight on to the base of the verb. L-extending verbs attach the -(으)러 ending to the EXTENDED base, for example 여-ㄹ- becomes 열러.
- 편지를 쓰러 위층으로 올라갔어요.He’s gone upstairs to write a letter.
- 친구를 만나러 역으로 나갔어요.He’s gone out to the station to meet a friend.
- 점심을 먹으러 식당에 가요.I’m going to the cafeteria to eat lunch.
- 술을 마시러 우리 집에 왔어요.They came to our place to drink (booze).
- 놀러 오세요.Come over sometime (to “play”, have fun, relax).
Purposive forms are made only with PROCESSIVE verb bases; there is no -(으)러 form for descriptive verbs, nor for the copula.