Feeling isolated or lonely due to absence of people or being alone
When to use
lack of people, inner isolation, social alienation
The nuance
외롭다 is used mainly for feelings arising from lack of human connection, focusing on inner sense of isolation.
외롭다 (oe-rop-da, oeropda) · 쓸쓸하다 (sseul-sseul-ha-da, sseulsseulhada)
외롭다 focuses on a feeling of isolation from lack of people, while 쓸쓸하다 relates more to a melancholic mood or atmosphere.

One lane per word — no nested boxes, just the gist.
Feeling isolated or lonely due to absence of people or being alone
When to use
lack of people, inner isolation, social alienation
The nuance
외롭다 is used mainly for feelings arising from lack of human connection, focusing on inner sense of isolation.
Feeling melancholic or empty due to a situation or atmosphere
When to use
melancholic mood, scene description, sentimental emptiness
The nuance
쓸쓸하다 is used for emotions felt from external situations or atmosphere, carrying a poetic or sentimental tone.
혼자 집에 있어서 너무 외롭다.
hon-ja jip-e iss-eo-seo neo-mu oe-rop-da., hon ja jip e iss eo seo neo mu oe rop da.
Appropriate for expressing isolation due to being alone.
혼자 집에 있어서 너무 쓸쓸하다.
hon-ja jip-e iss-eo-seo neo-mu sseul-sseul-ha-da., hon ja jip e iss eo seo neo mu sseul sseul ha da.
Suitable for expressing melancholic feeling in a lonely situation.
사람이 없어서 쓸쓸하다.
sa-ram-i eop-eo-seo sseul-sseul-ha-da., sa ram i eop eo seo sseul sseul ha da.
Can be used to express melancholic atmosphere due to lack of people.
사람이 없어서 외롭다.
sa-ram-i eop-eo-seo oe-rop-da., sa ram i eop eo seo oe rop da.
Appropriate for expressing inner isolation due to absence of people.
좋은 경치라서 외롭다.
joh-eun gyeong-chi-ra-seo oe-rop-da., joh eun gyeong chi ra seo oe rop da.
외롭다 is inappropriate here; use 쓸쓸하다 for feelings from scenery.
좋은 경치라서 쓸쓸하다.
joh-eun gyeong-chi-ra-seo sseul-sseul-ha-da., joh eun gyeong chi ra seo sseul sseul ha da.
Appropriate for expressing melancholic feeling from scenery.
친구가 없어서 쓸쓸하다.
chin-gu-ga eop-eo-seo sseul-sseul-ha-da., chin gu ga eop eo seo sseul sseul ha da.
외롭다 is correct for inner isolation due to lack of friends.
친구가 없어서 외롭다.
chin-gu-ga eop-eo-seo oe-rop-da., chin gu ga eop eo seo oe rop da.
Appropriate for expressing isolation due to absence of friends.
Which word suits expressing inner isolation when alone?
Which word describes melancholic feeling from a nice scenery or mood?
Which word fits feelings from having no friends?
What does it mean?