I guess English learners use some phrases like "I don't know" and "I don't understand" frequently. To emphasize that, people would use some adverbs, e.g. really.

Adverb usually comes after the auxiliary verb and before the main verb, so, that expression becomes

I don't really know ...

However, another option seems to be used as common

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Do they mean the same thing? Are they interchangeable in any cases? Could someone please give a hint? Thanks in advance.

3 Answers 3


Good question - they have quite an opposite meaning to most English speakers.

Saying "I really don't" makes your statement more emphatic.

On the other hand, "I don't really" softens it somewhat, and makes it less emphatic!

For example:

I really don't like carrots.

I would understand this to mean that the speaker definitely does not like carrots.

I don't really like carrots.

I would take this to mean they aren't keen on carrots, but may eat them if they have to!

There are multiple dictionary definitions of the word "really", and the two that support this contrast are:

  • used to emphasize a statement or opinion.
  • used to express mild protest.
  • Thank you! Would I consider "I really don't like carrots" is close to "I hate carrots" while "I don't really like carrots" not.
    – WXJ96163
    Commented Mar 24, 2020 at 9:56
  • @WXJ96163 Yes - politely saying you hate them, vs a preference against them.
    – Astralbee
    Commented Mar 24, 2020 at 10:04
  • Thank you so much. "I really don't like carrots" is a polite form of saying "I hate carrots". It also express a preference against them. Is my understanding right?
    – WXJ96163
    Commented Mar 24, 2020 at 10:16

To my understanding:

"I don't know" means you have strictly no understanding of what the speaker is talking about.

While "I don't really know" means you have some vague knowledge about the matter but not sufficient to answer the person who is speaking to you.

  • And "I really don't know" means that you really have no understanding of what the speaker is talking about - that is, you're making an even more emphatic claim than "I don't know". Commented Mar 24, 2020 at 9:03

The adverb "not" can modify either the verb phrase "know" or the adverb "really"

The syntax tells us what the meaning is. "I don't really know" means "not really", And so it is understood to mean "I partly understand".

Whereas "I really don't know" we have "not know", which is strengthened by the adverb really. And so it is understood to mean "I have no understanding."

So the two phrases are both quite common, but have opposite meanings.

If you asked me about French politics I would say "I don't really know much" But if you asked me about Uzbek politics of the 13th century I would say "I really don't know anything!"

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