면 오르다

if X, it goes up

오르다 is to rise, and in these four lines what rises is a figure rather than a person climbing: 오르면 내리고 여기가 내리면 오르고 'when one goes up the other comes down', 흉작이고 그러면 오를 수 있지 'a bad harvest can push it up'. The -(으)면 gives the trigger. For a person going up stairs or a hill you would hear 올라가다 instead.

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