If one says "I don't know" in 3 different ways, like, when they stress "I", "don't" and "know" respectively. How does the meaning of this sentence change?
When you put a stress on "I" in "I don't know," you're actually making a distinction between who you are talking about: "I" don't know! (not him, her, etc.)
When "don't" is stressed, it is meant to emphasize the negativity of the sentence: I "don't" know! (in contrast with "I know!").
And finally when you put a stress on the verb "know," you're emphasizing what you don't do: I don't "know"! (in contrast with, say, I don't "want" or I don't "like"!)
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Put another way, emphasis on “I” is equivalent to “Don’t ask ME” or Search ME”. It is non-committal as to whether anyone else knows. “I DON’T know” needs context. It could be a response to “I’m sure know what happened next”. No, I DON’T (know).”. I might have said don’t know already and you insist I must know. Then I stress the auxiliary. 3 depends on context. You might declare I don’t know my children, so I say (incredulously, “I don’t KNOW them?” Or it could be that you keep repeating the same question, till finally I say I don’t KNOW!” (exasperatedly). – Tuffy Aug 21 '19 at 14:03
I don’t know. Someone else knows it. It’s true that somebody knows it, but I am not that person.
I don’t know. That’s not true at all. Somebody has accused me and I’m protesting my innocence.
I don’t know. I only can suggest a possibility. In some way, I hint that, but I don’t have exact knowledge.
