er det det det er

You might think the title of this node is a bit odd, but it is actually a perfectly good sentence in Norwegian ... and Danish (thanks, liveforever) ... and in Swedish as well, but then spelled "är det det det är" (thanks, achtung man)

Er det det det er? means "Is that what it is?

Broken down to it's elements:

"Er det" is an introduction leading to a question: "Is it...."

the second "det" refers to "it" (Is it it)

The third "det" refers to the original object that is enquired about

The sentence "Er det det det er?" is mostly used in an affirmative way, with the second det stressed. In this case, it is usually used about a question that has been nagging you for a long time. When you finally get the answer, "Er det det det er?" expresses sort of a relieved request for final confirmation.

It might be worth noting that this sentence isn't just a grammatical oddity - it is actually in regular use.

i.e:

- Hvorfor er alle disse menneskene i gatene? (Why are all these people in the streets?)
- Det er 17. mai - nationaldagen! (It's the 17th of may - the national day of Norway!)
- Er det det det er? (is that what it is?)
- ...

This is a common sentence construction in Danish & Norwegian. However, as you might imagine, rare instances occur which can be even more grammatically confusing, such as in the following sample conversation:

Person A: Der er et overflødigt ord i din tekst. ("There is a superfluous word in your text.")

Person B: Hvilket ord er det? ("Which word is that?")

Person A: Det 'det' der, i tredje linie. ("That 'that' there, in the third line.")

Person B: Det 'det' der? ("That 'that' there?", pointing.)

Person A: Nej, det der. ("No, that there.", pointing.)

Person B: Nååå, er det det 'det' det er? ("Ahh, I see, is it that 'that' which it is?")

I've added quote marks around the proper det, to indicate how to parse this curious sentence.

Any language will contain grammatical absurdities like this, because of the inherent property of language: that it can be self-referential.