9岁女孩用英语怎么说

9岁女孩用英语可以说作 "a nine-year-old girl"。这个说法的来源是通过将年龄数字用英文表达，然后添加后缀 "-year-old"，最后加上 "girl"。
一些英文例句和中文翻译如下：
The nine-year-old girl is very smart.
这个9岁女孩很聪明。
She is a nine-year-old girl who loves to read.
她是一个喜欢读书的9岁女孩。
The nine-year-old girl is the youngest in her class.
这个9岁女孩是她班上最小的。