Relative Case inside the Clause | Esperanto Grammar

The case of relative kiu comes from its role inside the relative clause—not from the form of the noun it describes. This single principle explains contrasts such as la viron, kiu venis and la viro, kiun mi vidis. In the first, the antecedent is an object but kiu is a subject; in the second, the antecedent is a subject but kiun is an object.

English often hides this distinction because who, whom, which, and that do not consistently show case in everyday speech. Esperanto marks the internal structure explicitly with -n or with a preposition.

Two clauses, two independent roles

Analyze the main clause and relative clause separately:

Mi renkontis la kuraciston, kiu laboras nokte.

I met the doctor who works nights.

This combines:

Mi renkontis la kuraciston. The doctor is the object of renkontis, so kuraciston takes -n.
La kuracisto laboras nokte. The doctor is the subject of laboras, so relative kiu has no -n.

Now reverse the roles:

La kuracisto, kiun mi renkontis, laboras nokte.

The doctor whom I met works nights.

This combines La kuracisto laboras nokte with Mi renkontis la kuraciston. The antecedent la kuracisto is the main-clause subject, while kiun is the object of renkontis inside the relative clause.

💡

Temporarily replace the relative pronoun with the antecedent. Mi renkontis la kuraciston gives object kiun; la kuracisto laboras gives subject kiu. Then restore the relative form.

The four basic forms

Number agrees with the antecedent; accusative case reflects the internal role:

Form	Number	Role inside relative clause	Model
kiu	singular	subject or non-object	la gasto, kiu venis
kiun	singular	direct object	la gasto, kiun mi invitis
kiuj	plural	subject or non-object	la gastoj, kiuj venis
kiujn	plural	direct object	la gastoj, kiujn mi invitis

Mi salutis la gastojn, kiuj atendis ĉe la enirejo.

I greeted the guests who were waiting at the entrance.

La gastoj, kiujn mi salutis, atendis ĉe la enirejo.

The guests whom I greeted were waiting at the entrance.

The first happens to contain gastojn and kiuj, while the second has gastoj and kiujn. There is no rule requiring the endings to match. Each form belongs to a different clause.

Subject relative: kiu or kiuj

Use nominative kiu/kiuj when the relative pronoun performs the finite verb’s action or occupies another role that does not require -n:

Ni aĉetis lampojn, kiuj uzas malmulte da elektro.

We bought lamps that use little electricity.

Although lampojn is accusative in the main clause, the lamps are the subject of uzas. Therefore the relative pronoun is kiuj, not kiujn.

The relative subject can govern its own complements:

Mi serĉas iun, kiu povas helpi al la novaj volontuloj.

I am looking for someone who can help the new volunteers.

Here kiu is the subject of povas helpi; al la novaj volontuloj is a separate complement of helpi.

Object relative: kiun or kiujn

Add -n when the relative pronoun is the direct object inside its clause:

Jen la formularo, kiun vi devas subskribi.

Here is the form that you must sign.

The internal clause is vi devas subskribi la formularon. The object belongs semantically to the infinitive subskribi, but it is still a direct object and therefore appears as kiun.

Mi ne trovis la mesaĝojn, kiujn Nora sendis hieraŭ.

I did not find the messages that Nora sent yesterday.

Plural -j comes from la mesaĝojn; accusative -n comes from Nora sendis ilin. The combined ending is therefore -jn.

Object marking is retained even when flexible word order places kiun before the subject. Esperanto does not infer the role only from position.

Prepositional roles

If the antecedent would appear after a preposition in the relative clause, put that preposition before kiu/kiuj:

La kolego, kun kiu mi laboras, translokiĝos al alia urbo.

The colleague I work with will move to another city.

Jen la temoj, pri kiuj ni parolos morgaŭ.

Here are the topics that we will talk about tomorrow.

The underlying clauses are mi laboras kun la kolego and ni parolos pri la temoj. English commonly strands the preposition at the end—the colleague I work with. Neutral Esperanto places it before the relative pronoun: kun kiu, not kiu … kun.

Ordinary prepositions normally block accusative object -n:

La kliento, al kiu mi sendis la fakturon, jam pagis.

The client to whom I sent the invoice has already paid.

Do not write al kiun. Al already marks the recipient relation. The same applies to kun kiu, pri kiuj, de kiu, and most other ordinary prepositions.

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After an ordinary preposition, first write the same phrase you would use independently—kun ŝi, pri ili, al li—then replace the pronoun with kiu/kiuj: kun kiu, pri kiuj, al kiu.

Direction after spatial prepositions

Spatial prepositions that allow directional -n preserve that contrast with relative kiu:

Tio estas la domo, en kiu miaj geavoj loĝas.

That is the house in which my grandparents live.

Tio estas la domo, en kiun ili translokiĝis pasintjare.

That is the house into which they moved last year.

En kiu marks location; en kiun marks movement into the house. This -n is directional, not direct-object case. With inherently directional al, no extra -n appears: la urbo, al kiu ni veturas.

The dedicated discussion of optional directional marking is on prepositions with optional directional -n.

The main noun can have any role

The antecedent can be a subject, object, or prepositional complement in the main clause without changing the internal calculation:

Mi pensas pri la propono, kiun la komitato diskutos vendrede.

I am thinking about the proposal that the committee will discuss on Friday.

The antecedent is inside pri la propono in the main clause. Inside the relative clause, however, the committee will discuss the proposal directly, so use kiun.

La proponon, pri kiu ni parolis hieraŭ, la komitato nun akceptis.

The proposal we talked about yesterday, the committee has now accepted.

Here la proponon is fronted as a main-clause object, while pri kiu reflects ni parolis pri la propono. Free main-clause word order changes neither calculation.

Coordination inside relative clauses

When two relative clauses describe the same antecedent, each relative form follows its own internal role:

Mi dungis la kandidaton, kiu bone konas la programon kaj kiun la teamo rekomendis.

I hired the candidate who knows the software well and whom the team recommended.

The candidate is the subject of konas but the object of rekomendis, so kiu changes to kiun. Repeating the relative pronoun makes the parallel structure explicit. Omitting it as English often does would leave the second clause without its object and connector.

Tense and mood do not decide case

Case comes from grammatical role, while verb form expresses time or modality:

Ŝi montris al mi la ĉambron, kiun ni uzos morgaŭ.

She showed me the room that we will use tomorrow.

Past montris and future uzos are independently chosen. Kiun remains the object of uzos regardless of tense.

Ni bezonas solvon, kiun ĉiuj povu uzi sen speciala trejnado.

We need a solution that everyone can use without special training.

Volitive povu presents usability as a desired requirement. It does not remove object marking from kiun. In a factual statement—la solvo, kiun ĉiuj povas uzi—real mode is appropriate.

Questions, negation, and conversation

Ĉu tiu estas la teknikisto, al kiu vi telefonis?

Is that the technician you phoned?

Mi ne konas iun, kiu povus traduki la dokumenton hodiaŭ.

I do not know anyone who could translate the document today.

Neither the outer question nor main-clause negation changes relative case. In the first, telefoni al iu requires al kiu. In the second, the unknown person is the subject of povus traduki, so use kiu.

— Kiun dosieron vi bezonas? — Tiun, kiun vi sendis al mi ĉi-matene.

— Which file do you need? — The one that you sent me this morning.

The first kiun is interrogative and is the object of bezonas. The second is relative and is the object of sendis. Identical form does not mean identical clause function.

Punctuation and placement

Case endings do not show which noun a distant relative clause describes. Keep the clause next to its antecedent. A comma is a clear default before the finite relative clause; PMEG notes accepted variation in which some writers omit commas around tightly identifying clauses. Punctuation never changes kiu to kiun: only the internal role does.

In a long sentence, expand or reword rather than forcing the listener to retain an unresolved kiu across several clause boundaries. Clear international prose prefers an explicit antecedent and a nearby relative clause.

Common Mistakes

1. Copying the antecedent’s case onto a relative subject.

❌ Mi vizitis la amikon, kiun loĝas apud la stacidomo.

Incorrect — the friend is the subject of loĝas inside the relative clause.

✅ Mi vizitis la amikon, kiu loĝas apud la stacidomo.

I visited the friend who lives near the station.

2. Omitting -n from a relative object.

❌ La libro, kiu mi mendis, alvenis hodiaŭ.

Incorrect — the book is the object of mendis.

✅ La libro, kiun mi mendis, alvenis hodiaŭ.

The book that I ordered arrived today.

3. Adding -n after al.

❌ La kuracisto, al kiun mi skribis, respondis tuj.

Incorrect — al already marks the recipient relation.

✅ La kuracisto, al kiu mi skribis, respondis tuj.

The doctor to whom I wrote replied immediately.

4. Stranding the preposition as in English.

❌ La kolego, kiu mi laboras kun, ferias ĉi-semajne.

Incorrect — place kun before the relative pronoun.

✅ La kolego, kun kiu mi laboras, ferias ĉi-semajne.

The colleague I work with is on vacation this week.

5. Losing plural -j on an object relative.

❌ Mi kontrolis la fakturojn, kiun vi sendis.

Incorrect — the relative pronoun represents plural fakturojn.

✅ Mi kontrolis la fakturojn, kiujn vi sendis.

I checked the invoices that you sent.

Key Takeaways

Calculate the antecedent’s main-clause role and the relative pronoun’s internal role separately.
Kiu/kiuj are subjects; kiun/kiujn are direct objects.
Put a required preposition before the relative form: kun kiu, pri kiuj, al kiu.
Spatial prepositions can retain directional -n: en kiu for location, en kiun for motion into.
Tense, mood, word order, negation, and punctuation do not replace the internal case calculation.

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