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companion; partner; company
other party; addressee; counterparty
opponent (sports, etc.)
相手の話をよく聞こう。
Let's listen carefully to the other person.
試合の相手はとても強いチームだった。
The opponent in the match was a very strong team.
彼女は理想の結婚相手を探している。
She is looking for an ideal marriage partner.