Examples: I know (about) this difficulty/problem. I know (about) Engineering. In the first sentence, it seems to me that "to know" expresses that the speaker experienced the problem/difficulty before while "to know about" only expresses that the speaker has heard or read about it.
Possibly, "I do know that" can in fact only be used, when, you are answering the question of whether or not you know the issue at hand (or your knowledge has been called in to question, and you are answering that challenge). Let's say "out of the blue" you wanted to state that "you know that" -- and you wanted an emphatic version.
I saw this sentence in the book 1Q84: It's not just you that don't know. However, I am having trouble figuring out why (or whether) this is the correct way to write the sentence, as opposed to: ...
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Recently one of my friends told me that there is distinct difference between 'know of something' and 'know about something' expressions. 'know of' is used when you have personal experience with wha...
"Know about" vs. "know of" - English Language & Usage Stack Exchange