jestli, zda, and -li: 'whether/if'

English has two words here — "whether" and "if" — and uses them almost interchangeably for embedded yes-no questions ("I don't know whether/if he's coming"). Czech has three, and they differ chiefly by register: jestli (everyday), zda / zdali (formal, written), and the enclitic -li (literary, bookish). All three answer the same need: to embed a yes-no question inside another clause. The first thing to lock down, though, is what they are not: they are not že ("that"). Mixing up "whether" and "that" is the number-one error English speakers make with this construction.

What these words are for: embedded yes-no questions

A direct yes-no question — Přijde? ("Is he coming?") — becomes an indirect (embedded) question when you tuck it inside another clause: "I don't know whether he's coming." The embedded question needs a conjunction to introduce it, and that conjunction is jestli / zda / -li. Unlike English, the word order inside is the ordinary statement order (no inversion), and — as everywhere in Czech — the comma before the conjunction is obligatory.

For the mechanics of embedding a question in general, see indirect questions.

jestli — the everyday choice

jestli is the default, all-purpose "whether/if" in speech and casual writing. If you learn only one of the three, learn this one — it is never wrong in conversation.

Notice in the last example that the reported verb keeps its original tense — this is the no-backshift rule at work inside an embedded question.

jestli doubles as a colloquial "if" in real conditions, overlapping with když. This is the same jestli you meet on the conditional sentences page:

zda / zdali — the formal "whether"

zda (and its slightly fuller variant zdali) means the same as jestli but belongs to a formal, written register (formal). It is at home in reports, official letters, journalism, and careful prose. In everyday conversation it can sound stiff or over-educated.

Note that zda is only the "whether" word — it does not slide into conditional "if" the way jestli does. You would not use zda to mean "if you can, help me." Keep zda for embedded questions.

-li — the literary enclitic

-li is the most elevated option: a clitic that attaches directly to the verb (or the first stressed word) with a hyphen, in literary and formal-written style (literary). You'll meet it in older texts, set phrases, legalese, and elevated prose — rarely in speech.

The word order is distinctive: the verb comes first with -li clipped onto it (Bude-li…, Máte-li…), where speech would say Jestli bude…, Jestli máte…. Recognise -li, and use it only when you are deliberately writing in a formal or literary key.

The register ladder

Line the three up and the choice becomes mechanical: pick by how formal the context is.

The scale runs jestli < zda < -li from most everyday to most bookish. Using zda or -li in casual chat sounds like reading from a legal notice; using jestli in a formal report is acceptable but a touch plain.

The big trap: "whether" is NOT že

This is the error to eliminate first. English "if" and "that" both start with a small word, and learners reach for že ("that") when they mean "whether." But že introduces a statement, while jestli/zda introduce a question. "I don't know if he's coming" is a hidden question (is he coming? — I don't know), so it must be jestli, never že.

The test: can you rephrase the English with "whether"? "I don't know whether he's coming" — yes → jestli/zda. "I know whether he's coming" is odd; "I know that he's coming" is right → že. The že vs jestli split maps exactly onto statement-vs-question. For the fuller že picture, see complement clauses.

Don't confuse this "if" with unreal kdyby

There is one more "if" in Czech that does not belong here: kdyby, the hypothetical if of unreal conditions ("if I were rich…"). The jestli/zda "if" is either an embedded question or a real condition; the hypothetical "if" is kdyby + conditional. Keep them apart: Nevím, jestli přijde (whether) vs Kdyby přišel, byl bych rád (if he came — but he probably won't). The unreal kdyby is covered on the conditional sentences page.

Common Mistakes

Key Takeaways

• jestli / zda / -li all mean "whether/if" for embedded yes-no questions — the difference is register: jestli (everyday) < zda/zdali (formal) < -li (literary).
• jestli is the safe default in speech and also serves as colloquial "if" in real conditions.
• -li is an enclitic that attaches to the verb: Bude-li pršet…, Nevíš-li… — literary only.
• "Whether/if" is never že: že introduces a statement (Vím, že přijde), the others a question (Nevím, jestli přijde).
• This "if" is not the hypothetical kdyby — that one takes the conditional and belongs to unreal conditions.