为什么要说the/a two-year-old boy 不能说two years old boy

来源：学生作业帮编辑：百度作业网作业帮分类：英语作业时间：2024/06/06 17:42:02

因为two years old ,是三个单词组合成的一个短语,这个短语相当于名词性质,而two-year-old 是三个单词组成中间分别与-连接成的一个短语,这个短语相当于形容词的性质,而boy这个单词是名词性质,前面可以用形容词性质的单词跟短语修饰boy.
例如说,一颗三年的小树苗,可以说：three-year-old little tree,而不说three-years-old little tree或者three years old little tree,但可以说：little tree is three years old.
two-year-old 这个形容词类的词组的结构是：量词+名词（单数形式)+形容词.
至于前面的定冠词the或者不定冠词a,也是起修饰boy的作用,用the的话,就是前文已经提及过或者作者特指的,用a就是泛指“一个”了.
有不懂的地方,欢迎继续提问
再问：那么he is two years old 这里算名词性短语吗、是不是等于 he is a two-year-old boy 呢
再答：你问的好，he is two years old 是一个完整的句子不是名词性短语。什么是完整的句子呢？即：主语+谓语+宾语，这个只是简单的句子结构。复杂的就不说了。 He is two years old 等于 He is a two-year-old boy ，它们两个都是完整的简单句子。单词是由26个字母组合的，而短语或者词组或者固定搭配也是由名词性单词跟名词性单词或者动词性单词跟介词等等其他的组合形式组合成的至于那个the\a,也是起到修饰boy的作用，要看你是特指还是泛指了。不懂的地方，欢迎继续问

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