I don't know

• (US) IPA^(key): [ɑ̈ɪ̯ ɾoʊ̯(ʔ)(t̚) noʊ̯]

  • Audio (Mid-Atlantic)

    (file)

• (tonal) IPA^(key): [ə̃ː˦˩˦], [mː-], [-˩˥˨]

• Audio (UK)

  (file)

• Rhymes: -əʊ

I don't know

1. Used in response to a question or command in which the target person does not know the answer to or how to respond.
   • 1982, “You Can't Do That on Television”, in Nickelodeon, season 3, episode 11:

     Mr. Schidtler: Does anybody here have any idea why "Inestine" was regarded as a great scientist? Kevin?
     Kevin: Oh, uh, I don't know.

2. Used to indicate that one is speculating (often used sarcastically when stating the obvious).

   Maybe you could, I don't know, directly talk to her about it instead of complaining to me for once?

3. (UK) Used to express exasperation or incredulity about a given situation or person.

   The audacity of that lad... I don't know.

4. Used other than figuratively or idiomatically: see I,‎ don't,‎ know.
   • 1984, Alasdair, You Can't Do That on Television, Nickelodeon, season 5, episode 24:

     I don't know why Blip just shuts off the power and then blames it on the weather.

• I know

• dunno
• iunno