名词前应用定语修饰，一下有5种情况
形容词作定语：
The little boy needs a blue pen.(little修饰名词boy；blue修饰名词pen.）/小男孩需要一支兰色的钢笔。
Tom is a
handsome boy./Tom是个英俊的男孩。
There is a good boy./有个乖男孩。
数词作定语相当于形容词：
Two boys need two pens./两个男孩需要两支钢笔。
The two boys are students./这两个男孩是学生。
There are two boys in the room./房间里有两个男孩。
代词或
名词所有格作定语：
His boy needs Tom\'s pen./他的男孩需要Tom的钢笔。
His name is Tom./他的名字是汤姆。
There are two boys of Toms there./那儿有Tom家的两个男孩。
介词短语作定语：
The boy in the classroom needs a pen of yours./教室里的男孩需要你的一支钢笔。
The boy in blue is Tom./穿兰色衣服的孩子是汤姆。
There are two boys of 9,and three of 10./有两个9岁的，三个10岁的男孩。
名词作定语：
The boy needs a ball pen./男孩需要一支
圆珠笔。
It is a ball pen./这是一支圆珠笔。
There is only one ball pen in the pencil box./这铅笔盒里只有一支圆珠笔。
副词作定语：
The boy there needs a pen./那儿的男孩需要一支钢笔。
The best boy here is Tom./这里最棒的男孩是Tom。
不定式作定语：
The boy to write this letter needs a pen./写这封信的男孩需要一支钢笔。
The boy to write this letter is Tom./将要写这封信的男孩是汤姆。
There is nothing to do today./今天无事要做。
分词（短语）作定语：
The smiling boy needs a pen bought by his mother./那个微笑的男孩需要一支他妈妈买的钢笔。
The pen bought by her is made in China./她买的笔是中国产的。
There are five boys left./有五个留下的男孩。
希望能帮到你^_^！