英语中,否定形式有时直接加not,有时加don't,能详细分析下么?

在be动词和have做有的情况下,否定形式直接在后面加not
例如：I am a student.否定句：I am not a student.
I have money.否定句：I have no money.
其他实意动词在一般现在时的情况下,在动词前面加don't
例如：I study hard.否定句：I don't study hard.
但是实意动词在一般现在时态下,如果主语是三人称单数,在动词前面就要 加doesn't
例如：She works hard.否定句：She doesn't work hard.
希望能够帮到楼主

not与don't是英语中否定句的两种构成方法，当肯定句中有be动词,情态动词变成否定句，只需在这些词的后面加not就可以了，相反当肯定句中没有这些词时，变否定句需要在主语后面加
She is beautiful. She is not(isn"t) beautiful.
I can run. I can not (can"t)...

实义动词，借助于助动词否定，如don't，didn`t等
be动词或情态动词，直接加not

其实don't 就是do not 的缩写哦。几乎所有的否定形式都是加not的。
例：
I can't (can not ) do it .
I haven't (have not ) do it .
I don't (do not )know it .
I didn't (did not )know it .
we aren't (are not )there .
he isn't (is not) my cousin.