편의점 가는 김에 네 것도 사 올게

The line, explained

In K-dramas, affection is often shown through tiny favours. Someone is heading out, and on the way they ask, 'Want anything?'. Korean has a grammar pattern built exactly for this: -는 김에, 'while I'm at it, since I'm doing this anyway'. It tags an extra action onto one you are already doing. Today's line comes from a roommate scene, late at night, when one person grabs their keys and offers to pick something up for the other.

편의점 is 'convenience store', from 편의, 'convenience', and 점, 'shop'. The spelling has 의, but after a consonant it is pronounced like 이, so you hear pyeo-ni-jeom. Korean has an astonishing number of these stores, open all night, and they show up in dramas as reliably as cafés. 가는 is from 가다, 'to go', in the present modifier form. It needs that form because 김 is a noun, and 가는 describes it.

김 is a small noun meaning roughly 'opportunity, the moment, the occasion'. 김에 is 'on the occasion of'. 가는 김에 is therefore 'on the occasion of going', which English renders as 'since I'm going anyway'. The tense in the modifier matters: -는 김에 for something happening now or about to happen, -(으)ㄴ 김에 for something already done. 온 김에 means 'since you're already here', and 말 나온 김에 means 'since it's come up'.

네 것도 is 'yours too': 네 (your), 것 (thing) and 도 (also). In casual speech 것 often becomes 거, so you will also hear 네 거도 or 니 것도. 사 올게 is two verbs chained: 사다, 'to buy', and 오다, 'to come', meaning 'buy and bring back'. The ending -ㄹ게 is the promise form, 'I'll do it for you'. Put it all together and the offer is complete, warm and very practical.

Swap the errand and the pattern keeps working: 마트 들르는 김에 네 것도 사 올게 (since I'm stopping by the mart), 커피 사러 가는 김에 네 것도 사 올게 (since I'm getting coffee), 밖에 나가는 김에 네 것도 사 올게 (since I'm heading out). It is equally at home in requests: 일어난 김에 물 좀 줘 (since you're up, get me some water). Learn it and you will hear it in every household scene from now on.