USAGE NOTE 用法说明: hyphens
Use a hyphen (-) to join two or more words that are used as an adjective in front of a noun. 名词前作形容词用的两个或两个以上单词之间用连字符（-）连接:
a two-car family 拥有两辆车的家庭
a ten-year-old boy 一个十岁的男孩。
You can also say 还可以这么说:
a family with two cars 拥有两辆车的家庭
a boy who is ten years old 一个十岁的男孩