In a relative clause, Esperanto chooses kiu or kiun according to the relative word’s role inside that clause. The case of the preceding noun—its antecedent—does not control the case of the relative. Compare Mi renkontis la kuraciston, kiu helpis vin with La kuracisto, kiun mi renkontis, helpis vin.
This independence is the central rule. English often hides it because “who,” “that,” and zero relative pronouns do not visibly mark object case. Esperanto makes the relationship explicit with -n and does not normally omit the relative word.
Kiu as subject, kiun as object
Start by expanding the relative clause into a separate sentence:
Mi renkontis la kuraciston, kiu helpis vin.
I met the doctor who helped you.
The two underlying statements are Mi renkontis la kuraciston and La kuracisto helpis vin. Although la kuraciston is an object in the main clause, the relative kiu replaces the subject of helpis, so it has no -n.
Now reverse the inner roles:
La kuracisto, kiun mi renkontis, helpis vin.
The doctor whom I met helped you.
The relative clause expands to Mi renkontis la kuraciston. The doctor is the object of renkontis, so the relative form is kiun. The antecedent la kuracisto is the main-clause subject and remains unmarked.
Number comes from the antecedent; case comes from the inner role
Relative kiu agrees in number with the people or things it represents, while its case comes from its own clause:
| Antecedent | Role inside relative clause | Form |
|---|---|---|
| singular | subject | kiu |
| singular | object | kiun |
| plural | subject | kiuj |
| plural | object | kiujn |
La volontuloj, kiuj organizis la eventon, alvenis frue.
The volunteers who organized the event arrived early.
La volontulojn, kiujn ni elektis, tre ŝatas la tuta teamo.
The whole team really likes the volunteers whom we selected.
In the second example, la volontulojn is an object in the main clause, and kiujn is independently an object inside the relative clause. The matching endings happen because both roles are objects—not because one mechanically agrees with the other.
The two case patterns can diverge in either direction:
Mi legis la artikolon, kiu aperis hieraŭ.
I read the article that appeared yesterday.
La artikolo, kiun mi legis hieraŭ, enhavis gravan eraron.
The article that I read yesterday contained an important error.
Esperanto does not omit the object relative
English readily says “the book I bought,” leaving out “that.” Standard Esperanto keeps the relative word:
Jen la libro, kiun mi aĉetis en la stacidomo.
Here is the book I bought at the station.
The form Jen la libro, mi aĉetis en la stacidomo is not a standard relative construction; it sounds like two clauses run together and leaves the object relation unmarked. PMEG explicitly advises not to omit relative kiu. This rule applies in conversation as well as writing.
— Ĉu tio estas la filmo, kiun vi rekomendis? — Jes, sed mi ne memoras la nomon de la reĝisoro.
— Is that the film you recommended? — Yes, but I don't remember the director's name.
Even though English translation naturally omits “that,” Esperanto retains kiun because it is the object of rekomendis.
Prepositions replace object case
If the represented participant is a complement whose preposition itself supplies the relation inside the relative clause, put that preposition before kiu and use no object -n:
La kolegino, kun kiu mi laboras, loĝas proksime.
The colleague I work with lives nearby.
Jen la kliento, al kiu mi ankoraŭ ne respondis.
Here is the client whom I have not yet replied to.
Kun kiu and al kiu correspond to labori kun ŝi and respondi al li. The English preposition may appear at the end or disappear in a loose translation, but Esperanto places it before the relative.
La propono, pri kiu ili diskutis, ne estis akceptita.
The proposal they discussed was not accepted.
Because the frame is diskuti pri io in this meaning, the form is pri kiu, not pri kiun. Ordinary prepositions already mark the role. Spatial prepositions are the important separate case because directional -n may independently apply; that pattern appears below. The dedicated relative case page develops this choice further.
Kio, kion, and clauses without a noun antecedent
Relative kio normally refers to an indefinite thing, a correlative such as io/ĉio/nenio, or the content of a preceding statement—not to an ordinary noun that would take kiu. It takes -n when it is an object inside its clause:
Mi aŭdis ion, kion mi ne povas klarigi.
I heard something that I cannot explain.
Ŝi nuligis la vojaĝon, kion neniu atendis.
She canceled the trip, which nobody expected.
In the first, kion represents ion as object of klarigi. In the second, kion refers to the whole preceding event and is object of atendis. If the relative itself were the subject, the form would be kio: Okazis io, kio ŝanĝis mian opinion.
Do not spread the -n of kion onto a separate predicative adjective:
Mi ne trovis ion, kion mi konsiderus vere utila.
I did not find anything that I would consider truly useful.
Here kion is the object of konsiderus, but utila is its predicative description and therefore does not take -n. By contrast, Mi ne trovis ion utilan has utilan directly inside the object phrase.
Kies is invariable, but the possessed phrase shows its own case
Relative kies means “whose” and never takes -n. The noun phrase it determines may nevertheless be an object:
Mi renkontis la aŭtoron, kies novan libron vi ĵus recenzis.
I met the author whose new book you just reviewed.
Kies marks the possessor. Novan libron is the object of recenzis, so adjective and noun take -n. Writing kiesen or kiesn would violate the correlative system.
Directional and measure -n in a relative are not object -n
Place relatives use kie; directional -n produces kien:
La urbo, kien ni translokiĝos, estas multe pli malgranda.
The city we are moving to is much smaller.
Kien marks a destination. It is not a direct object of translokiĝos. Compare static La urbo, kie ni nun loĝas... “The city where we now live...” The same distinction can appear after a spatial preposition: la domo, en kiun ŝi kuris “the house she ran into,” with directional -n after en.
A relative can also inherit a measure role inside its clause:
La dek kilometroj, kiujn ni marŝis matene, lacigis ĉiujn.
The ten kilometers that we walked in the morning tired everyone.
Here kiujn represents la dek kilometrojn in the underlying clause ni marŝis la dek kilometrojn. Its -n marks extent, not an object affected by marŝis. Relative forms therefore preserve all ordinary uses of -n, not only object case.
Norm, variation, and style
Fundamenta examples already establish kiu/kiun/kiuj/kiujn with case determined inside the relative clause. PMEG states the rule explicitly and rejects omission of relative kiu as a national-language calque. This is stable foundational norm.
Word order within the relative clause remains flexible—kiun mi elektis and, in a suitable contrast, kiun elektis mi are possible—but case must remain visible. Very remote or heavily nested relatives are grammatical yet can be hard to process; clear neutral prose keeps the relative close to its antecedent.
Common Mistakes
1. Copying the antecedent’s case onto the relative.
❌ Mi vidis la virinon, kiun laboras ĉi tie.
Incorrect — the woman is the subject of laboras inside the relative clause.
✅ Mi vidis la virinon, kiu laboras ĉi tie.
I saw the woman who works here.
2. Forgetting object -n inside the relative clause.
❌ La mesaĝo, kiu mi ricevis, estis malplena.
Incorrect — the relative is the object of ricevis.
✅ La mesaĝo, kiun mi ricevis, estis malplena.
The message I received was empty.
3. Omitting the relative word as English does.
❌ Jen la foto, vi sendis hieraŭ.
Incorrect — Esperanto requires an explicit object relative.
✅ Jen la foto, kiun vi sendis hieraŭ.
Here is the photo you sent yesterday.
4. Adding -n after an ordinary preposition.
❌ La temo, pri kiun ni parolis, estas sentema.
Incorrect — pri already marks the relation.
✅ La temo, pri kiu ni parolis, estas sentema.
The topic we talked about is sensitive.
5. Forgetting plural before accusative.
❌ La kandidatoj, kiun ni intervjuis, havis sperton.
Incorrect — the plural antecedent requires kiujn.
✅ La kandidatoj, kiujn ni intervjuis, havis sperton.
The candidates whom we interviewed had experience.
Key Takeaways
- The relative’s case comes from its role inside the relative clause, independently of the antecedent.
- Kiu/kiuj mark relative subjects; kiun/kiujn mark relative objects.
- Standard Esperanto does not omit an object relative as English often omits “that.”
- Prepositional relatives use forms such as kun kiu and pri kiu, without object -n.
- Kion can be an object relative; kien has directional, not object, -n.
Related Topics
- Case and Number on CorrelativesA2 — Learn exactly which correlative families accept plural -j, object -n, or directional -n, and which remain invariant.
- Relative Clauses with KiuA2 — How kiu, kiuj, kiun, and kiujn introduce finite clauses that identify or describe people and things.
- Relative Case inside the ClauseA2 — How the case and preposition of kiu are determined inside the relative clause, independently of the antecedent’s role.
- Kies in Relative ClausesB1 — Use kies to connect a person or thing with something belonging to it, including the subject or object behind an action noun.
- Kie, Kiam, and Kiel as RelativesB2 — Build relative clauses of place, time, and manner with kie, kiam, and kiel, including directional and prepositional variants.