This is the 1317th most frequent Korean word.
둘째
"Second" or "the second one."
Here, '둘째' is used as an adjective to describe the ordinal position of the child in a sequence.
나는 둘째 아이와 함께 공원에 갔습니다.
I went to the park with my second child.
'둘째로' is used as an adverb to indicate the sequence order of the topic being discussed, as the second item.
이번 회의에서 둘째로 중요한 주제를 논의했습니다.
In this meeting, we discussed the second most important topic.
'둘째' is used as a noun representing the second child in the context of familial indexing.