A content question asks the listener to supply missing information: a person, thing, kind, owner, place, time, reason, manner, or quantity. Esperanto marks that missing category with one of nine ki-correlatives. The system is more regular than English who, what, where, when, and how many, but you must choose the ending by meaning and give the question word the grammatical form its role requires.
One ki- series, nine kinds of answer
The beginning ki- marks a question or a relative link. In a direct question, the ending tells the listener what kind of answer is wanted.
| Question word | Information requested | Typical answer |
|---|---|---|
| kiu | which individual; who | la nova kuracisto |
| kio | what thing, matter, or event | la paneo |
| kia | what kind; what quality | trankvila kaj hela |
| kies | whose; belonging to whom | de Ana |
| kie | where; at what place | ĉe la stacidomo |
| kiam | when; at what time | morgaŭ matene |
| kial | why; for what reason | pro la pluvo |
| kiel | how; in what manner or degree | per la metroo |
| kiom | how much or how many | tri |
— Kiu telefonis al vi tiel malfrue? — Mia frato.
— Who called you so late? — My brother.
Kio okazis al la interreto?
What happened to the internet?
Kiam vi povos sendi la finan version?
When will you be able to send the final version?
— Kial la trajno haltis? — Pro arbo sur la trako.
— Why did the train stop? — Because of a tree on the track.
This is a closed, foundational system, not a list of freely invented compounds. Learn the nine endings as semantic categories. The dedicated table-word system page shows how the same endings combine with ti-, i-, ĉi-, and neni-.
Kiu, kio, and kia answer different questions
English who and what do not map word for word onto Esperanto. Kiu selects an individual, human or nonhuman. Kio asks about an unspecified thing, matter, event, role, or definition. Kia asks for a quality or kind.
Kiu estas ĉe la pordo? — La nova najbaro.
Who is at the door? — The new neighbor.
Kio estas tiu aparato? — Portebla ŝargilo.
What is that device? — A portable charger.
Kia estas la nova najbaro? — Tre afabla kaj iom parolema.
What is the new neighbor like? — Very kind and a little talkative.
The contrast is especially clear with people:
Kiu ŝi estas? — Ŝi estas doktoro Marin.
Who is she? — She is Dr. Marin.
Kio ŝi estas? — Ŝi estas kuracisto.
What is she? — She is a doctor.
Kia ŝi estas? — Ŝi estas pacienca kaj rekta.
What is she like? — She is patient and direct.
The first asks identity, the second role or profession, and the third character or quality. This three-way division is productive and cannot be recovered from English what alone.
The question word has a role inside the clause
A ki-correlative is not an external label pasted onto a sentence. It fills the missing grammatical slot. If kiu, kio, or kia is a direct object, it takes accusative -n. Kiu and kia can also take plural -j, with -n after -j when both are required.
Kiu invitis Leon?
Who invited Leo?
Kiun Leon invitis?
Whom did Leo invite?
The forms alone identify the roles: kiu is the subject in the first question; kiun is the object in the second.
Kiujn fotojn vi volas presi?
Which photos do you want to print?
Kion vi serĉas en la kuirejo?
What are you looking for in the kitchen?
For motion toward a place, kie can take directional -n:
Kie vi atendos nin?
Where will you wait for us?
Kien vi iros post la koncerto?
Where will you go after the concert?
Most other ki-correlatives do not take -j or -n. See case and number on correlatives for the complete distribution.
Keep a preposition with its ki-phrase
When the missing information has a prepositional role, put the preposition before the question word. Esperanto does not normally strand a preposition at the end as conversational English does.
Kun kiu vi vojaĝos al Prago?
Who will you travel to Prague with?
Pri kio ili diskutis dum la paŭzo?
What did they discuss during the break?
Ĝis kiam la oficejo restos malfermita?
Until when will the office remain open?
The whole unit—kun kiu, pri kio, ĝis kiam—normally stands at the beginning of its question clause. This is a major English-to-Esperanto adjustment: build the role first, then place the complete ki-phrase initially.
Kiom da before a noun
Use kiom alone for an amount or number whose category is already clear. Before an expressed noun, use kiom da + noun. The noun after da does not take accusative -n, because da already marks its relation to the quantity.
Kiom kostas la taga bileto?
How much does the day ticket cost?
Kiom da gastoj jam respondis?
How many guests have already replied?
Kiom da akvo ni bezonas por la supo?
How much water do we need for the soup?
Do not copy English how many as two independent words. Kiom already means “what quantity”; da links that quantity to the measured substance or counted category.
Content questions are not ĉu questions
Ĉu presents a complete proposition and asks whether it is true. A ki-question contains a missing constituent and asks the listener to supply it.
Ĉu vi renkontos ŝin post la laboro?
Will you meet her after work?
Kiam vi renkontos ŝin?
When will you meet her?
The first can be answered jes or ne. The second needs a time. Do not combine both markers in the same clause. They may occur in one sentence only when they introduce different clauses:
Ĉu vi scias, kiam la vendejo fermiĝas?
Do you know when the shop closes?
Here ĉu marks the main yes-no question, while kiam begins the embedded content question. Learn the basic polar pattern on Yes-No Questions with Ĉu.
Word order and conversational variation
The foundational norm is to put the ki-word or complete ki-phrase at the beginning of its own clause. The remaining words generally keep normal Esperanto order; there is no English-style subject–auxiliary inversion and no question-forming “do.”
Kie via fratino laboras nun?
Where does your sister work now?
In lively (informal) conversation, a ki-word can remain at the end as an echo question expressing surprise or demanding confirmation:
— Mi mendis dekdu picojn. — Vi mendis kiom?!
— I ordered twelve pizzas. — You ordered how many?!
This final position is accepted and well attested for echo questions, but it is strongly marked. It is not the neutral template for asking ordinary information. Multiple ki-words are also possible; normally only one must be initial:
Kiu sendis kion al kiu?
Who sent what to whom?
Negative content questions
Negation does not change the question system. Keep the ki-word initial and place ne before the verb or constituent it negates.
Kial vi ne respondis al mia mesaĝo?
Why didn't you answer my message?
Kiu ankoraŭ ne ricevis sian nomŝildon?
Who still hasn't received their name badge?
If the expected answer itself is negative, Esperanto may use a negative correlative: neniu, nenio, nenie, and so on. One such NENI- form normally makes the whole clause negative. Several NENI- forms can sometimes reinforce one negation, but adding ne to a NENI- form normally creates logical double negation instead. That broader system belongs on negative correlatives.
Common Mistakes
1. Adding ĉu to a content question.
❌ Ĉu kie estas la necesejo?
Incorrect — ĉu and kie cannot mark the same question clause.
✅ Kie estas la necesejo?
Where is the restroom?
2. Copying English do-support or inversion.
❌ Kiam faras la filmo komenciĝi?
Incorrect — Esperanto does not translate question-forming ‘does.’
✅ Kiam la filmo komenciĝas?
When does the film begin?
3. Forgetting the object ending on the question word.
❌ Kiu vi invitis al la festo?
Incorrect — the person asked about is the direct object.
✅ Kiun vi invitis al la festo?
Whom did you invite to the party?
4. Stranding a preposition as in informal English.
❌ Kiu vi parolis kun?
Incorrect — kun must introduce its complement.
✅ Kun kiu vi parolis?
Who did you speak with?
5. Using kiu when the question asks for a quality.
❌ Kiu estas via nova apartamento? — Hela kaj kvieta.
Incorrect — the answer describes a quality, not an individual's identity.
✅ Kia estas via nova apartamento? — Hela kaj kvieta.
What is your new apartment like? — Bright and quiet.
Key Takeaways
Choose kiu, kio, kia, kies, kie, kiam, kial, kiel, or kiom by the information requested. Put the complete ki-phrase at the beginning, mark its grammatical role with case or a preposition, and keep ordinary clause order after it. Use ĉu only when the missing answer is yes or no—not when a ki-correlative already asks for the missing content.
Related Topics
- Yes-No Questions with ĈuA1 — Form yes-no questions with ĉu while keeping normal clause order, clear negation, and unambiguous answers.
- Question Word OrderA1 — Place ĉu and ki-phrases correctly while preserving ordinary Esperanto clause order and clear grammatical roles.
- Indirect QuestionsB1 — Embed yes-no and content questions with ĉu or a ki-correlative while preserving Esperanto word order, case, and intended tense.
- The Table-Word SystemA1 — Learn Esperanto's 45 table words as a five-by-nine meaning system for questions, demonstrations, indefinites, universals, and negatives.
- Case and Number on CorrelativesA2 — Learn exactly which correlative families accept plural -j, object -n, or directional -n, and which remain invariant.
- Ke, Ĉu, or a Ki-Word?C1 — Choose ke for a proposition, ĉu for an unresolved yes-or-no question, and a ki-word for an open information slot inside an embedded clause.