This is the 1585th most frequent Japanese word.
妹
Younger sister.
Here, '妹' refers to the speaker's own younger sister and is used as a direct reference.
私の妹は学校に通っています。
My younger sister goes to school.
In this sentence, '妹' still refers to the speaker's own younger sister, emphasizing the familial relationship and helpful action.
妹が宿題を手伝ってくれました。
My younger sister helped me with my homework.
Here, '妹' describes the younger sisters of another person, showcasing its use to refer to someone else's siblings.