• 姉妹しまい — sisters
• 義姉ぎし — sister-in-law
• 姉御あねご — big-sister figure / bossy woman
• 姉上あねうえ — elder sister (honorific)
• 実姉じっし — biological older sister
• 姉ねえさん — older sister (polite / familiar)

姉 combines 女 (woman) with 市, which once suggested rank or status. The character came to represent a mature or respected woman — and by extension, one’s older sister.

It is commonly used when talking about one’s own family and often carries a sense of closeness, respect, or affection.