A female who has the same parents with another person, or who has one of them only. In the latter case, she is more definitely called a half sister. The correlative of brother.
- A female having the same parents as another or one parent in common with another.
- A girl or woman who shares a common ancestry, allegiance, character, or purpose with another or others, specifically:
- A kinswoman.
- A woman fellow member, as of a sorority.
- A fellow woman.
- A close woman friend or companion.
- A fellow African-American woman or girl.
- A woman who advocates, fosters, or takes part in the feminist movement.
- Informal Used as a form of address for a woman or girl.
- Ecclesiastical A member of a religious order of women; a nun.
- Ecclesiastical Used as a form of address for such a woman, alone or followed by the woman's name.
- Chiefly British A nurse, especially the head nurse in a ward.
- One identified as female and closely related to another: "the sisters Death and Night” ( Walt Whitman).
- Related by or as if by sisterhood; closely related: sister ships; sister cities.
- Genetics Of or being one of an identical pair: sister chromatids.