区别就在于:3-year-old就相当于一个形容词来使用,意为“三岁的”,后面接名词。3 years old后面通常不接成分,一般放在be动词后面。例句:He is a 3-year- old boy.他是一个三岁的男孩。She is 3 years old.她三岁。
3-year-old是形容词,放在名词前。3 years old需放在连系动词(is am are )后面
3- year- old 作定语,后面接名词。
Mhmmdhkkj