妹

1. Origins, structure, and basic meaning

• Structure: 妹, read いもうと, means a female sibling younger than the reference person.
• Basic usage: Possession can be stated as 私の妹, and 妹と marks the younger sister as a companion in an action. The family context identifies whose sibling she is.

2. Common pitfalls and similar expressions

• A female sibling who is younger
  • This identifies a female sibling younger than the reference person, whether cooking dinner together or starting high school. It does not mean someone else's older sister.