우리가 걷던 그 길에 혼자 서 있어

The line, explained

Every Korean breakup song has a place in it. A street, a bus stop, a bench by the river. The place is the same; the person is gone. This line is the purest version of that image, and it depends on one syllable, -던, which turns 'the road' into 'the road we used to walk'. Learn -던 and every empty street in K-pop starts to make sense, because you can finally hear what the singer is standing in: not a location but a memory.

우리가 is 'we' as the subject: 우리, we, plus 가. In a breakup song 우리 is heavy, because it names a unit that no longer exists. 걷다 is to walk, and 걷던 is that verb wearing -던, the retrospective modifier. It goes in front of a noun and describes it by a past, ongoing action: the road that we used to walk, the road we were always walking. English needs five or six words for what -던 does in a single syllable.

The important comparison is with -(으)ㄴ, the plain past modifier you may already know. 걸은 길 would be 'a road that was walked', a single completed fact. 걷던 길 is 'the road we used to walk', a habit, a stretch of time, something that was still going on when the memory stopped. -던 attaches to any bare stem the same way: 듣던 노래, the song I used to listen to; 사랑하던 사람, the person I used to love; 앉던 자리, the seat you always sat in.

그 길에 is 'on that road'. 그 is that, 길 is road or path, 에 marks the place. 그 instead of a name keeps it universal; every listener supplies their own road. 혼자 means alone, by oneself. 서 있어 is 서다, to stand, in the -아/어 있다 form, which describes a state that results from an action: not 'I stand' but 'I am standing there'. The whole line is a still photograph with one person in it and room for two.

Say it slowly, because the line is slow: u-ri-ga geot-deon geu gi-re, hon-ja seo i-sseo. Many singers pause after 길에, letting the place sit before the loneliness arrives. Now swap the memory and keep the road: 우리가 달리던 그 길에 혼자 서 있어, the road we used to run; 우리가 웃던 그 길에, the road where we used to laugh. -던 makes each one a place that remembers.