신경 literally means “nerve”, that organ with neurons in your body. But I typically hear 신경 used with the verb 쓰다. 신경쓰다 can be translated “to care” or “to care about”, according to 데미안’s blog on Naver. The verb 쓰다 also means “to use”, so I like to picture marshaling a bunch of neurons for some purpose. 데미안 gives a bunch of examples, including:
I don’t care. / 난 신경 안 써.
But 신경쓰다 can also be translated “to worry”, as in the example:
제발 완벽하게 되려는 것에 신경쓰지마. / Please don’t worry about being perfect.
(데미안 translates this example somewhat unnaturally as “Please don’t care about being perfect.”)
고민, according to my favorite dictionary of the moment 한국어-영어 학습 사전, means “A state of being agonized and bothered due to a worry on your mind.”
Here’s an example I put to my favorite native Korean speaker:
고민할 때는 신경을 많이 쓴다.
How would you translate that? I came up with a few options:
- When I’m agonized, I marshal a lot of neurons for the purpose. (too literal)
- When I’m worried, I care a lot. (maybe)
- When I’m worried, I get really nervous. (maybe)
When in doubt, sometimes I go to the hanja. Dan Bravender’s koreanhanja.app site is pretty intuitive. The 고 in 고민 is from the Chinese 苦 meaning “bitter; hardship, suffering”. The 민 comes from 悶, meaning “gloomy, depressed, melancholy”. So 고민 gives the feeling of anguish more than plain old worry. The key difference between 신경쓰다 and 고민하다 seems to be that 고민 makes the pain and suffering explicit, whereas 신경 can refer to any run-of-the-mill worry or care. It’s the difference between worrying and agonizing about something.
Naver dictionary example #1 for 고민 is:
여러 가지 복잡한 문제로 고민하다 보니 머리가 아프다.
You can see the pain clearly in this example (머리 아프다).
Now for a 신경 example from Naver:
이 일 저 일 하도 신경을 쓰다 보니 지쳐서 잠이 퍼부어 왔다.
The subject was tired or fed up from doing this and that, so he fell asleep right away. I suspect that without the verb 지치다, added to convey that the speaker was tired or fed up, this sentence would be ambiguous in terms of the subject’s suffering.