noun
one matter; one item; one case
Used to count or refer to a single matter, item, or case, often in formal, business, or news contexts. Functions as a noun with a built-in counter meaning.
この一件はまだ解決していない。
This matter has not been resolved yet.
先日の一件についてお詫び申し上げます。
I apologize for the incident the other day.