doesn't 和 isn't 是 does 和 is 的否定词（或反义词）,因此 doesn't / isn't 的用法和 does / is 一样, 也就是He/she/itdoesn't 表达动作,即 他/她/它 "做" 或“操作” 某某事,通常接动词。
例：He doesn't go sailing anymore, ever since his boating accident.
译：自从出事以来，他再也不去航海了。
例：He isn't a carefree person that he used to be, ever since the mishap.
译：自从那次灾难以来，他并不像以前那样无忧无虑。
isn't和doesn't的用法一样，都常用于否定句。在很多情况下，两者可以互换。
如：But he is not reading his newspaper tonight.
这里的is not可以用doesn't代替，表达的意思都是但他今晚不看报纸。
词汇解析：
isn't：不是的
发音：英 [ˈɪznt] 美 [ˈɪznt]
is not 的常用口语形式
例：It isn't too difficult once you get the idea.
译：你一旦弄懂了，就不太难了。
doesn't：不是的；不
发音：英 [ˈdʌznt] 美 [ˈdʌznt]
does not 的常用口语形式
例：It doesn't matter to me whether you go or not.
译：你去或不去，对我都没关系。
