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I doubt that he will come tomorrow.

I am not sure that he will come tomorrow.

Please check these sentences.

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kumenglish

I doubt that he will come tomorrow.

I am not sure that he will come tomorrow.

Please check these sentences.

Both are OK.

Also, I'm not sure if he'll come tomorrow.

CJ

Comments  
kumenglishI doubt that he will come tomorrow.

You think he probably won't come.

kumenglishI am not sure that he will come tomorrow.

You can't guarantee that he will come.

 CalifJim's reply was promoted to an answer.