I just stumbled upon this sentence taken from a 1974 textbook on Esperanto published in Poland:

"Andreo kaj Mary promenis en la parko kaj dividis impresojn pri la bonega spektaklo, kiun ili partoprenis en la operejo."

And I cannot understand why there is kiun and not kion. It clearly refers to spektaklo, it is not used as a determiner, but as pronoun. And spektaklo is not a person but a thing. Is it an error or is there another exceptional rule governing the use of "kiu" and "kio" in Esperanto?

  • Welcome to Esperanto Language Stack Exchange! I'll have to look there more thoroughly, but bertilow.com/pmeg/gramatiko/subfrazoj/rilataj/kiu_kio_kies & its subchapters seem to imply that "kiu" is the default pronoun to introduce a relative subclause, while "kio" as a relative pronoun is only used when the conditions for certain rules that mandate "kio" instead of "kiu" are fulfilled.
    – das-g
    Commented Sep 3, 2023 at 22:33
  • I'm not that fluent in Esperanto. All I managed to auto-translate says something about "more abstract meaning of nouns". This doesn't explain anything. When the meaning of noun becomes "more abstract"? And what about relative clauses? There's an example "Mi volas, ke tio, kion mi diris, estu vera". Does it mean if I talk about abstract things, I should say "tio, kion mi diras", and when I talk about non-abstract things, it should be "tiu, kiu mi diras"? OK, but where the border after which what I'm saying becomes abstract enough to use "kio"? And isn't Esperanto becoming overcomplicated here?
    – Peter82
    Commented Sep 6, 2023 at 20:31

2 Answers 2



Das-g mentioned a chapter of PMEG that explains the differences between relative kio and kiu. The subchapter about kio lists four main cases when kio is used.

1. when referring to a correlative ending to -o

      ● Mi volas, ke tio, kion mi diris, estu vera.

Note that this correlative can also be implicit.

      ● Oni ricevas, kion oni bezonas. = Oni ricevas tion, kion oni bezonas.

2. when a noun is left out

      ● La sola, kion mi deziras, estas… = La sola afero, kiun mi deziras, estas…

3. when referring to a whole clause

This causes the following distinction:

      ● Julio Cezaro venkis la pontanojn kaj gajnis gloron, kio estis surprizo.

      ● Julio Cezaro venkis la pontanojn kaj gajnis gloron, kiu estis surprizo.

where kio refers to the whole preceeding clause and thereby the surprice was the victory and the glory following it. In the latter case kiu refers only to the glory and thereby the surprice was only it (even in the meaning that the surprice was the form of glory, a titel, a triumph, or some other reward).

Unfortunately this distinction is not observed by all.

4. when referring to an object of the same type

      ● Ili alvenis per aŭto, kion mi ankoraŭ ne havas, sed ja planas aĉeti.

Here aŭto does not refer to any specific car, but cars in general. If there were kiu, you would be planning to buy just that car.


As the last example above shows, the basic meaning of kiu is "one of a known set".

In your example

      …pri la bonega spektaklo, kiun ili…

the set can be thought to be all spektakloj and the relative pronoun kiun in the subclause refers to the one identified as the one in which Andreo and Mary participated in.

Note, that if no set is given, it is supposed to be "people, humans", and this meaning is used in questions:

  • Kiuj promenis en la parko?
  • Your answer does not make it clearer. I'm not a native speaker of English, so you'd need to explain, how do you understand "which". As I remember "which", as a relative pronoun, refers to objects, and its counterpart for people is "who". But "kiu"/"kio" distinction has nothing or very little to do with "person"/"non-person" difference. So, please never ever explain Esperanto function words. It rearely explains anything. And you haven't answered why "kio" is wrong there. Unless you mean "kio" refers to whole clauses, while "kiu" to words and phrases. Am I right?
    – Peter82
    Commented Sep 6, 2023 at 20:17
  • I am sorry that my answer was not clear. The key phrase is the "one of a known set". In order to illustrate that I rewrote my answer to cover all cases of kio. PS. Neither am I a native speaker of English. Commented Sep 7, 2023 at 7:34

Indeed kiun is correct, and kion less so. kion is not necessarily referencing spektaklo as with tio, kion, but more of the main phrase. Like what in:

..., kio estis la unua paŝo de interrilato.

kiu meaning which (adjective) can only reference spektaklo. Like in:

pri tiu spektaklo, kiun ...

However this is linguistics on an advanced level. More congruent to some European languages.

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