姉が

older sister

→ 姉
phrase Uncommon #12,526
older sister 姉 means “older sister,” and が marks her as the subject of the clause. 姉 is used when talking about your own older sister; お姉さん is commonly used for someone else’s older sister.
JA: 姉が本を読んでいます。
EN: My older sister is reading a book.

一番上の姉が母の代わりをした。

My oldest sister took my mother’s place.

ある晩家にいたら-帰宅した姉が変だった

One night, while I was at home, my older sister came home acting strangely.

— Carandiru (2003)

私は姉が入学試験に受かることを望んでいる。

I hope my older sister passes the entrance exam.

来年の春、姉が結婚します。

My older sister is getting married next spring.

私の両親は姉が外国人と結婚するのに反対している。

My parents are opposed to my older sister marrying a foreigner.

姉が僕に新しい時計を見せてくれた。

My older sister showed me her new watch.

私が留守の間、姉が犬の世話をしてくれた。

My older sister took care of my dog while I was away.

姉が死んで私が引き取ったと

That her older sister died, and I took her in.

— すずめの戸締まり (2022)

私には姉が三人もいるのよ。

I have three older sisters!

姉が一番好きなのは漱石です。

My older sister's favorite author is Soseki.

うちの姉がついに結婚したんです。

My older sister finally got married.

私の義理の姉があなたの宿題を手伝ってくれるものをあてにしていいです。

You can count on my sister-in-law to help you with your homework.

姉が時々夕食を作る。

My older sister sometimes makes dinner.