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that; that thing
that person
then; that time
that place (over there)
down there (i.e. one's genitals)
period; menses
「彼」 has other readings with different meanings.
駅の向こうにあれは何の建物ですか。
What is that building?
彼はぐぶぐぶとうがいをした。
He gargled loudly.
テーブルの上にあれは私のかばんです。
That is my bag.