This is the 224th most frequent Korean word.
어느
"Which" (used to ask or refer to a specific one among choices).
'어느' is used to ask about selecting something specific within a group or category.
이 근처에 어느 레스토랑이 가장 맛있나요?
Which restaurant around here is the most delicious?
'어느' is used to indicate an unspecified or certain instance of a noun, in this case, 'day'.
어느 날 갑자기 그가 방문했어요.
One day, he suddenly visited.
'어느' is used to inquire about a choice among distinct possibilities, here among directions.