A formal or written expression equivalent to における, used to indicate location, time, or context. Often appears in academic or official language.
See also: における
Economic growth in Japan has been slowing in recent years.
His position on this issue is clear.
Rarely used kanji form; mainly encountered in formal or older texts.
Derived from the verb 置く (おく, 'to place') in its classical attributive form 置ける, which grammaticalized into a formal locative/temporal marker. The kanji 於 is an ateji borrowing from Chinese.