Choose the embedded-clause introducer from the kind of content being embedded. Ke presents a proposition—a statement, belief, fact, wish, or reported claim. Ĉu leaves the truth of a whole yes-or-no proposition unresolved. A ki- word leaves one particular participant, place, time, reason, manner, or quantity unresolved and also fills a grammatical role inside its clause.
English often uses omitted that, ambiguous if, or broad question words, so its surface form is a poor guide. Diagnose the information structure first.
The three-way decision
| Embedded content | Introducer | Underlying independent form |
|---|---|---|
| proposition presented or entertained as a statement | ke | La trajno malfruos. |
| yes-or-no issue | ĉu | Ĉu la trajno malfruos? |
| open information slot | appropriate ki- word | Kiom da minutoj la trajno malfruos? |
Mi aŭdis, ke la trajno malfruos.
I heard that the train will be late.
Mi ne scias, ĉu la trajno malfruos.
I do not know whether the train will be late.
Mi ne scias, kiom da minutoj la trajno malfruos.
I do not know how many minutes late the train will be.
The first embeds a report. The second asks for a yes/no answer. The third assumes a delay as the context and leaves its extent open.
Ke embeds a proposition
A ke clause packages a complete proposition as a subject, object, complement, or description. It does not mark that proposition as a question. The ke-clause guide treats its full distribution; here the important issue is choosing it against the two interrogative patterns.
La administranto konfirmis, ke la sistemo denove funkcias.
The administrator confirmed that the system is working again.
Estas evidente, ke ni bezonas pli klaran planon.
It is obvious that we need a clearer plan.
Ni esperas, ke la kuracisto permesos al vi iri hejmen morgaŭ.
We hope that the doctor will let you go home tomorrow.
The proposition can be asserted, reported, desired, feared, or evaluated. Ke marks its clause type, not the speaker’s certainty. Even a denied belief still takes ke when the content is statement-like.
Mi ne kredas, ke tiu ŝlosilo malfermas la malantaŭan pordon.
I do not believe that that key opens the back door.
Unlike English that, Esperanto ke is normally expressed. Omitting it can make two finite clauses collide or suggest direct quotation.
Ŝi diris, ke ŝi revenos antaŭ la vespermanĝo.
She said that she would return before dinner.
Esperanto does not backshift the subordinate tense merely because diris is past; revenos still locates the return after the saying.
Ĉu embeds a polar question
Use ĉu when the unresolved information is the truth of the entire proposition: yes or no, it happened or it did not, the alternative holds or it does not.
Bonvolu kontroli, ĉu la fenestroj estas ŝlositaj.
Please check whether the windows are locked.
Neniu demandis, ĉu mi bezonas helpon.
Nobody asked whether I needed help.
— Ĉu vi scias, ĉu Mara jam alvenis? — Ne, ŝi ankoraŭ ne skribis.
— Do you know whether Mara has arrived yet? — No, she has not written yet.
The first ĉu in the exchange marks the direct main question “Do you know?” The second marks the embedded question “Has Mara arrived?” Repetition is not redundant because each operates at a different clause level.
English if is dangerous here. Embedded interrogative “if/whether” is ĉu; conditional “if” is se.
Mi sciigos vin, ĉu la propono estos akceptita.
I will let you know whether the proposal is accepted.
Mi sciigos vin, se la propono estos akceptita.
I will notify you if the proposal is accepted.
In the first sentence, the listener will receive the answer either way. In the second, acceptance is the condition under which notification will occur.
A ki-word embeds an open question
Use the ki- correlative matching the missing information:
- kiu/kio for identity or thing;
- kies for possessor;
- kie/kiam for place or time;
- kial/kiel for reason or manner;
- kiom for quantity or degree;
- kia for kind or quality.
Mi volas scii, kiu ŝanĝis la pasvorton.
I want to know who changed the password.
Ĉu vi memoras, kie ni lasis la aŭton?
Do you remember where we left the car?
La kuracisto klarigis, kial la dozo devas esti malpliigita.
The doctor explained why the dose has to be reduced.
The ki- word is not merely a conjunction. It performs a role inside its own clause, and its form follows that role.
Mi ne scias, kiun dosieron ŝi forigis.
I do not know which file she deleted.
Mi ne scias, kiu dosiero malaperis.
I do not know which file disappeared.
In the first clause, kiun dosieron is the object of forigis and takes -n. In the second, kiu dosiero is the subject of malaperis. The main verb scias does not determine this case; the embedded clause does.
One main verb can accept all three
The selecting verb often does not choose the introducer by itself. Scii, rimarki, kontroli, malkovri, and similar verbs can embed different content types.
Mi malkovris, ke la dosiero estis kopiita.
I discovered that the file had been copied.
Mi kontrolis, ĉu la dosiero estis kopiita.
I checked whether the file had been copied.
Mi malkovris, kiu kopiis la dosieron.
I discovered who copied the file.
The intended discourse task—not an English dictionary entry—selects the clause type. A speaker reporting a conclusion uses ke; a speaker investigating truth uses ĉu; a speaker identifying a missing participant uses kiu.
Do not stack introducers
An embedded question begins directly with ĉu or the needed ki- word. It does not also take ke.
Mi ne certas, ĉu la butiko ankoraŭ estas malfermita.
I am not sure whether the shop is still open.
Mi ne certas, kiam la butiko fermiĝas hodiaŭ.
I am not sure when the shop closes today.
Forms such as ke ĉu, ĉu kie, and ke kial normally reveal that the learner translated an English frame before deciding what kind of embedded content is present.
There can be coordinated questions: Mi volas scii, ĉu kaj kiam la plano estos publikigita asks both whether publication will happen and, if so, when. This is coordination of two legitimate interrogative dimensions, not stacked marking of one question.
Embedded questions are not direct questions
The embedded clause keeps interrogative meaning but functions as a part of the larger sentence. If the whole sentence is a statement, it ends with a period, not a question mark.
Mi demandis, kie troviĝas la plej proksima haltejo.
I asked where the nearest stop was.
Ĉu vi povas diri al mi, kie troviĝas la plej proksima haltejo?
Can you tell me where the nearest stop is?
Only the second whole sentence is a direct yes-or-no question. Esperanto does not use English-style subject–auxiliary inversion, so the internal word order remains transparent.
Interrogative and relative ki-clauses
A ki- word can also introduce a relative clause, where it refers back to an antecedent rather than opening a question. Compare:
Mi ne scias, kiu riparis la aparaton.
I do not know who repaired the device.
La teknikisto, kiu riparis la aparaton, laboras hodiaŭ.
The technician who repaired the device is working today.
The first asks for an identity. The second describes la teknikisto. Some free relative clauses, such as Prenu, kion vi bezonas, can be analyzed through a supplied meaning “take what you need,” but the practical rule remains: no antecedent plus an unresolved answer favors an embedded question; an expressed antecedent favors a relative clause.
Register and norm
All three patterns are foundational and neutral. Ke omission is common in English but is not the neutral Esperanto model. Ĉu rather than se for embedded polar questions is a firm standard distinction. A ki- word’s case and number follow its role inside its own clause.
In (formal) prose, long nested clauses may be replaced by a noun phrase or divided into shorter sentences for clarity. That is a style decision, not variation in the three-way grammatical contrast.
Decision flow
- Are you presenting, reporting, evaluating, fearing, or desiring proposition content rather than seeking an answer? Use ke.
- Is the unresolved answer simply whether a whole proposition is true? Use ĉu.
- Is one participant, place, time, reason, manner, kind, or quantity missing? Use the matching ki- word.
- Assign case and number to the ki- word from its role inside the embedded clause.
- If English uses “if,” distinguish embedded question ĉu from condition se.
Common Mistakes
Using ke before an embedded yes-or-no question
❌ Mi demandis, ke la biletoj ankoraŭ estas disponeblaj.
Incorrect — the speaker asked whether the proposition was true.
✅ Mi demandis, ĉu la biletoj ankoraŭ estas disponeblaj.
I asked whether the tickets were still available.
Copying English if as se
❌ Mi ne scias, se li partoprenos la kunvenon.
Incorrect — this is an embedded polar question, not a condition.
✅ Mi ne scias, ĉu li partoprenos la kunvenon.
I do not know whether he will attend the meeting.
Combining ĉu with a ki-word
❌ Ŝi demandis, ĉu kie ni aĉetis la lampojn.
Incorrect — kie already introduces the open place question.
✅ Ŝi demandis, kie ni aĉetis la lampojn.
She asked where we bought the lamps.
Omitting ke as English permits
❌ Mi pensas la nova horaro estos pli oportuna.
Incorrect — the two finite clauses need the statement introducer ke.
✅ Mi pensas, ke la nova horaro estos pli oportuna.
I think that the new schedule will be more convenient.
Taking the ki-word’s case from the main clause
❌ Mi ne memoras, kiu ni invitis al la vespermanĝo.
Incorrect — kiu is the direct object of invitis inside the embedded clause.
✅ Mi ne memoras, kiun ni invitis al la vespermanĝo.
I do not remember whom we invited to dinner.
Key Takeaways
Use ke for statement-like propositional content, ĉu for a yes-or-no issue, and a ki- word for a specific open slot. Build the embedded clause from its own internal syntax; do not copy English that/if or stack multiple introducers.
Related Topics
- Ke-ClausesA2 — How finite clauses introduced by ke function as statements, subjects, objects, complements, and content descriptions.
- Ĉu-Clauses as Embedded QuestionsA2 — How ĉu introduces a finite yes/no question functioning inside a larger sentence, distinct from ke statements and se conditions.
- Ki-Correlative Embedded QuestionsB1 — How kiu, kio, kia, kies, kie, kiam, kial, kiel, and kiom introduce finite questions embedded inside larger clauses.
- Indirect QuestionsB1 — Embed yes-no and content questions with ĉu or a ki-correlative while preserving Esperanto word order, case, and intended tense.
- Reported StatementsB1 — Report speech, thought, perception, and written information with finite ke-clauses while preserving the original tense and adjusting viewpoint clearly.
- Reported QuestionsB2 — Embed yes-no and content questions with ĉu or a ki-correlative while preserving finite clause structure, tense, case, and viewpoint.