Learn Hardcore Croatian: Ona sigurno zna odgovor.

Ona sigurno zna odgovor. (neutral)
Sigurno zna odgovor. (neutral, with initial adverb)
Sigurno ona zna odgovor. (contrastive emphasis on she: “She, of all people, surely knows the answer.”)

Avoid or use with care:

Ona zna sigurno odgovor. (unnatural in standard usage; prefer placing sigurno before the verb)
Don’t split clitics around it (see clitic note below).

What part of speech is sigurno, and how is it different from sigurna/siguran?

sigurno is an adverb meaning “surely/certainly” (and in other contexts “safely”).
siguran (masc.), sigurna (fem.), sigurno (neut.) are adjectives meaning “sure/certain/safe.”
Example: Ona je sigurna. = “She is sure.”

What verb form is zna, and how do I conjugate znati?

zna is 3rd person singular present of znati (to know). Present tense:

ja znam
ti znaš
on/ona/ono zna
mi znamo
vi znate
oni/one/ona znaju

Why doesn’t odgovor change form here? Which case is it?

It’s the direct object in the accusative singular. For masculine inanimate nouns, nominative and accusative have the same form, so odgovor looks unchanged.
Compare: nominative čovjek (man) → accusative čovjeka (animate masculine changes), but odgovor stays odgovor.

How do I say “the answer” vs “an answer” in Croatian?

Croatian has no articles. odgovor can mean either “the answer” or “an answer,” depending on context. To be explicit you can use:

taj odgovor (that/the specific answer)
neki odgovor (some/an answer)

How do I replace odgovor with a pronoun “it,” and where does the pronoun go?

Use the clitic ga (masc./neut. singular object) and put it in second position:

Ona ga sigurno zna.
Sigurno ga zna. Do not say: ✗ Ona sigurno ga zna (clitic in the wrong place). Clitics can’t start a sentence, so ✗ Ga sigurno zna is also wrong.

How do I turn this into a yes/no question?

Neutral yes/no: Zna li ona odgovor? or simply Zna li odgovor?
If you want “Is it certain that she knows the answer?”: Je li sigurno da ona zna odgovor?
Colloquial echo question with doubt: Ona sigurno zna odgovor? (rising intonation)

How do I negate it, and what’s the difference between sigurno ne and ne … sigurno?

Ona sigurno ne zna odgovor. = “It’s certain that she doesn’t know the answer.” (sigurno has wide scope over the negation.)
Ona ne zna (odgovor) sigurno. = “She doesn’t know (the answer) for sure.” Here sigurno modifies the manner of knowing (for sure), not your certainty about the whole statement. A clearer version is Ona ne zna sa sigurnošću.

Could sigurno mean “safely” here?

Not in this sentence—here it means “surely/certainly.” But elsewhere sigurno can mean “safely”: Vozim sigurno. = “I drive safely.”

What’s the difference between znati, poznavati, and saznati/doznati?

znati = to know (facts/information): Zna odgovor.
poznavati = to know/be acquainted with (people/things): Poznaje tu osobu.
saznati/doznati = to find out/learn (come to know): Saznat će odgovor. (She will find out the answer.)

How do I mention what the answer is to?

Use na: odgovor na pitanje (answer to a question).
Example: Ona sigurno zna odgovor na to pitanje.

How do I say this in the past or future, and where do auxiliaries go?

Past: Ona je sigurno znala odgovor. (je = auxiliary “to be” in 2nd position)
Future: Ona će sigurno znati odgovor. (će = future auxiliary in 2nd position)
With an object clitic: Ona ga je sigurno znala. / Sigurno ga je znala.

Is Ona zna sigurno odgovor acceptable?

It’s generally viewed as awkward. Prefer Ona sigurno zna odgovor.
If you mean “know for sure,” you can also say: Ona zna odgovor, sigurno. (afterthought) or Ona zna odgovor sa sigurnošću.

Any quick pronunciation tips for this sentence?

g is always hard, as in “go” (si-gu-rno).
Roll the r slightly: si-gu-rno.
Consonant clusters: zn in zna is pronounced z + n; dg in odgovor is d + g.
A safe stress approximation: stress near the beginning of each word (Ona, SÍgurno, Ódgovor). Native stress patterns vary regionally.

Are there synonyms for sigurno here, and do they all mean the same?

zasigurno = certainly/for sure (a bit more emphatic/formal)
svakako = certainly/by all means (often agrees to a suggestion)
naravno = of course (presumes obviousness)
They’re close but not identical in tone. sigurno is the most neutral for “surely/certainly.”