doubt后什么时候用if 何时用whether?

一般情况下doubt后面if和whether都可以用，比如：
I doubt if/whether he will come to my party.
但是如果后面是to do或者or not的话则需用whther,比如：
I doubt whether to come to his party.
I doubt whether he will come to my party or not.
如果是否定句的话则要用that，比如：
I don't doubt that he will come to my party.
希望对你有帮助

doubt 后面好像不应该用if or whether

你就记住。。什么时候用WHETHER都不会错。。。IF我记着好像只能引导宾语从句。。。他俩的确有区分。。不过用WHETHER永远都不会错

whether 后面可以加 or not if 不可以

1.doubt如果是动词引导宾语从句时,如果主句是肯定句,则宾语从句的引导词可用if/whether.
如：I doubt if/whether he is a student.
当然,如果此宾语从句中含有or/or not时,只能使用whether.
如：I doubt whether he is a student or not.
I doubt whether he is a student or a teacher.
另：doubt如果是动词引导宾语从句时,如果主句是否定句/疑问句,则宾语从句的引导词只能用that.
如：I don't doubt that he is a student.
2.doubt如果是名词引导同位语从句时,如果主句是肯定句,则同位语从句的引导词只能用whether.
如：I have doubt whether he is a student.
doubt如果是名词引导同位语从句时,如果主句是否定句/疑问句,则同位语从句的引导词只能用that.
如：There is no doubt that he is a student.