"姐姐" 在英语中翻译为 "elder sister" 或 "older sister"， "妹妹" 在英语中翻译为 "younger sister"。
来源：这两个词来源于汉语，在英语中有类似的词汇表达同样的意思。
例句：
"My elder sister is a doctor." (我姐姐是医生。)
"I have a younger sister who is in college." (我有一个在大学的妹妹。)
"My sister is older than me." (我姐姐比我年长。)
"My sister is younger than me." (我妹妹比我年轻。)