three-year-old这类词算哪个语法点

这类题易考复数形式的混淆
很多人都会写成three-years-old
这其实不算什么语法点,但是很容易考
其实它在句中做的是形容词成分
比如three-year-old boy 三岁的男孩

恩怎么说呢...
我只能说是一种数词连接型的定语吧.

一般会出在类似数词的考察中,考察点主要在量词后不加s

three-year-old为形容词,比如:
my three-year-old sister
three years old为单词组合,比如
my sister is three years old.

数词-量词（单数）-形容词

数词

是 属于数词