year old,year-old,years old,years-old的区别

year old只能是 He is only one year old.即years old的单数形式.years old就是一岁以上的了,例如She is three years old.year old 和 years old通常都作表语.首先要声明绝对没有years-old的说法,因为加上连接符以后...