托福 写作中，绝不是词汇就可以一统天下的，语法问题也是高分必需要攻克的一道难关，想要写出逻辑清晰，遣词造句正确丰满的高质量托福 作文，托福写作语法不可忽视。
一 基本规律(Basic rules)
1. Indefinite article (不定冠词)
我们用 "a ， an " 当我们不知道他是诸多人或事中的哪一个：
is one of many. ( 是许多个中的一个)
He is an artist.(=there are many artists)
is not unique. (不是唯一的)
I have just bought a book
has not been mentioned before. (之前没有提到过)
There was a new student in class today.
2. Definite article (定冠词)
我们用 " the " 当我们知道他是诸多人或事中的哪一个：
is unique (or unique in that context) (是唯一的)
The Australian Prime Minister. (=there is only one)
I looked inside， the engine was in
