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Hi, please help me.

I don't know that it is dangerous.
I don't know whether it is dangerous.

Do these sentences have different meanings?
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tashiroI don't know that it is dangerous.
I don't know whether it is dangerous.

Do these sentences have different meanings?
Yes, they do.

I don't know whether it's dangerous (and also I don't know if it's dangerous) say that you don't know the answer to the question "Is it dangerous?"

I don't know that it's dangerous can mean that you doubt that it's dangerous. It's like I'm not so sure that it's dangerous or I don't completely believe that it's really very dangerous.

I don't know that it's dangerous can also mean that nobody told you that it's dangerous. You have no hard evidence that it's dangerous.

CJ
Comments  
Hi! In a sense, "that" is more direct. Use "whether" when you are giving another option like: "I don't know whether it is dangerous or not."

Hope this helps.
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Thank you very much Emotion: smile
 CalifJim's reply was promoted to an answer.
Hey Thanks CJ ☺👍
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