"sister" 的意思是 姐妹。它可以指代与自己有相同父母的女性亲属，也可以用来形容与自己有亲密关系的女性朋友。此外，"sister" 还可以指代修女或女修道士。

造句示例：

1. She is my sister.

2. They are sisters.

3. Our school is her sister school.

4. The sisterhood of women is powerful.

5. She became a nun, a sister of the convent.