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older sister; elder sister
「姉」 has other readings with different meanings.
姉は来月結婚する予定だ。
My older sister is getting married next month.
子どもの頃は姉とよくけんかした。
I often fought with my older sister when I was a child.
姉に相談したら的確なアドバイスをもらえた。
When I consulted my sister, I got precise advice.