來看幾個例子吧!
一個10歲的男孩：
a ten years old boy.這里years old是固定搭配,前面是ten,所以用復(fù)數(shù).
a ten-year-old boy.這里ten-year-old是一個復(fù)合形容詞,中間有連詞符,所以year用單數(shù).
一些10歲的男孩子們
some ten years old boys.years old是固定搭配,通常前面是數(shù)字,year根據(jù)數(shù)字選擇用單數(shù)或復(fù)數(shù)
some ten-year-olds boys.old這里可看做是名詞,加s變復(fù)數(shù),
總結(jié)：復(fù)合形容詞 x-year-old修飾單數(shù),而x-year-olds修飾復(fù)數(shù).
OK?希望能幫到你啊!我是來自英語牛人團的 Ivy !