네가 웃을 때 세상이 멈춰

The line, explained

Every idol chorus needs one gloriously over-the-top compliment, and this is it. 네가 웃을 때 세상이 멈춰, 'when you smile, the world stops'. Big emotion, small grammar: the line hinges on -(으)ㄹ 때, which means 'when'. It marks the moment one thing happens, and the rest of the sentence tells you what happens at that time. You will meet this pattern in songs, in conversation and in fans' comments every day.

네가 is 'you' as the subject, often sung as 니가 so it is not confused with 내가 (I). 웃을 comes from 웃다, which means both to smile and to laugh. The stem 웃 ends in a consonant, so it takes -을, and the ㅅ slides forward when spoken: u-seul. Then comes 때, meaning 'time'. The ㄸ is a tense T, said sharply without a puff of air, so it sounds like ttae.

So 웃을 때 literally means 'the time of smiling'. The rule is simple: consonant stems take -을 때 (먹을 때, 웃을 때), vowel stems take -ㄹ 때 (볼 때, 갈 때), and stems already ending in ㄹ just add 때 (힘들 때, 놀 때). For a single finished moment in the past, slip in the past marker: 만났을 때, when we met. Add 마다 for 'every time': 볼 때마다, every time I see you.

세상이 is 'the world' as the subject. 세상 means the world, but in a lived-in, everyday sense: life, people, everything around you. 멈춰 is the casual form of 멈추다, to stop. The stem 멈추 meets the ending -어 and merges into 멈춰. Because Korean present tense covers habits, this does not just mean the world stopped once. It means it stops every single time you smile, which is the whole point of the compliment.

Sing it bright and light: ne-ga u-seul ttae, then a little drop for se-sang-i meom-chwo. Now try other moments: 네가 울 때, when you cry; 네가 날 볼 때, when you look at me; 네가 내 이름 부를 때, when you call my name. Then take it into real life: 힘들 때 전화해, call me when things are hard. That one is not a lyric, but it might be the kindest sentence in this lesson.