This is the 2500th most frequent Korean word.
때문인
"때문인" means "because of" or "due to."
In this sentence, '때문인' is used to explain the reason for 'he is angry.' It connects the cause (a misunderstanding) to the effect.
그가 화난 것은 오해 때문인 것 같아요.
He seems to be angry because of a misunderstanding.
Here, '때문인' introduces a specific reason (traffic jam) as the substantive cause of the delay.
교통 체증 때문에 늦은 것이 분명해요.
It is evident that the delay is due to traffic jam.
In this usage, '때문인' is used to hypothesize that the cold weather might be attributed to the flu.