This is the 8365th most frequent Korean word.
seoul
The capital city of South Korea.
In this sentence, the word '서울' is used to denote a proper noun, specifically the name of a place, which is the capital city of South Korea.
서울은 한국의 수도입니다.
Seoul is the capital of South Korea.
Here, '서울' refers to a location and is combined with the location marker '에서' to indicate the place where the action of living happens.
저는 서울에서 살아요.
I live in Seoul.
In this example, '서울의' describes possession, suggesting something belongs to or is associated with Seoul, in this case, the spring season.