This is the 14621st most frequent Korean word.
미성년자일
"미성년자일" means "to be a minor."
미성년자일 in this sentence is used to indicate the state of being a minor, appended with the particle '일'.
이 영화는 미성년자일 관람할 수 없습니다.
This movie cannot be watched by minors.
미성년자일 describes the condition or timeframe of being underaged, with '때' indicating 'when.'
미성년자일 때는 보호자가 필요합니다.
When you are a minor, a guardian is needed.
미성년자일 is used to hypothesize the possibility of being a minor, showing how '일 수 있다' can indicate potential state or condition.