Learn Hardcore Croatian: Tada smo pomislili da će ispit biti lak. - Then we thought that the exam would be easy.

tada is a bit more neutral or slightly more formal and precise, often used in narrative or written language.
onda is very common in everyday speech and can also mean so / in that case (for consequences), e.g. Onda idemo. = Then let’s go / So let’s go.

In your sentence, you could also say Onda smo pomislili da će ispit biti lak without changing the basic meaning.

What does smo mean in smo pomislili, and why is it in the middle of the sentence like that? Can the order change?

Smo is the auxiliary verb we are / we were from biti (to be), used to form the past tense.

pomislili is the past participle (thought),
smo tells you it’s we (1st person plural).

In Croatian, short auxiliary forms like smo, sam, si, and će are clitics. They normally go in the second position in the clause, so:

Tada smo pomislili… (first word = Tada, second position = smo)

You can change word order for emphasis, but the clitic position is quite rigid:

Mi smo tada pomislili… (OK)
Pomislili smo tada… (OK)
❌ Tada pomislili smo… (sounds wrong in standard Croatian)

So smo can move with the verb group, but it keeps that “second position” behavior.

Why is it pomislili and not mislili? What’s the difference between misliti and pomisliti?

Both come from the idea of thinking, but they differ in aspect and nuance:

misliti (imperfective) = to think in general, to be thinking, to have an opinion
- Mislili smo da je lak. = We thought / were thinking it is easy.
pomisliti (perfective) = to think something once, to come to think something at a particular moment (a single mental event)
- Tada smo pomislili… = At that specific moment, we (suddenly) thought…

So pomislili fits well here because it refers to a single moment when that idea occurred to you.

Why do we need da in pomislili da će ispit biti lak? Can we leave it out?

Da introduces a subordinate clause (a “that”-clause), just like that in English:

We thought that the exam would be easy.
Pomislili smo da će ispit biti lak.

Many Croatian verbs of thinking, saying, feeling, etc. (misliti, pomisliti, reći, vjerovati, nadati se) normally take a da + clause:

Rekao je da će doći. = He said (that) he would come.

You cannot simply say ❌ Pomislili smo će ispit biti lak. The da is required here.

In English we say “We thought the exam would be easy,” but Croatian uses će biti (future) – da će ispit biti lak. Why future, not something like a conditional?

Croatian often keeps real future tense after past-tense verbs of thinking and saying, even where English uses would:

Mislio sam da će padati kiša. = I thought it would rain.
literally: I thought that it will rain.

The logic is: at that past moment (tada), the exam was still in the future, so Croatian uses normal future I (će biti) in the subordinate clause.

You can use the conditional (bi) in different shades of meaning, e.g. more hypothetical:

Mislili smo da bi ispit mogao biti lak. = We thought the exam might be easy.

But for a straightforward “We thought the exam would be easy (when it happens)”, da će ispit biti lak is the usual choice.

Why is it da će ispit biti lak and not something like da ispit će biti lak? Where exactly does će go?

Će is another clitic (short auxiliary) for future tense, so it follows the same second position rule within its own clause.

In the clause da će ispit biti lak:

first element: da
second position: će
then: ispit biti lak

You can say:

Mislili smo da će ispit biti lak. (standard, natural)
❌ Mislili smo da ispit će biti lak. (wrong word order; će is not in the usual clitic slot)

If you remove da, in an independent clause you’d typically get:

Ispit će biti lak. (first word Ispit, second position će)

So: će usually comes right after the first stressed word (or after da in a da-clause).

What case is ispit here, and why doesn’t it change form?

Ispit is in the nominative singular here, because it’s the subject of the subordinate clause:

(da) će ispit biti lak = (that) the exam will be easy.

Croatian doesn’t have articles like a / the, so ispit covers both an exam and the exam, depending on context. It stays in its base form (nominative) because it’s just the subject, not an object or after a preposition.

Could I say Tada smo mislili da će ispit biti lak instead of Tada smo pomislili…?

Yes, Tada smo mislili da će ispit biti lak is grammatically correct.

The nuance is:

Tada smo pomislili… = At that moment we suddenly/once had the thought that…
Tada smo mislili… = Around that time we thought / used to think / were of the opinion that…

So pomisliti sounds more like a single moment of realization, while misliti can describe an ongoing opinion.

Why is biti needed in će ispit biti lak? Can I say da će ispit lak without biti?

You cannot drop biti here.

In Croatian, when you say that something is / will be / was + adjective, you must use a form of biti:

Ispit je lak. = The exam is easy.
Ispit će biti lak. = The exam will be easy.
Ispit je bio lak. = The exam was easy.

So ❌ da će ispit lak is incorrect; you need biti to link ispit and lak.

What’s the difference between lak and lagan? Could I say da će ispit biti lagan?

Yes, you can say da će ispit biti lagan; it’s also correct and natural.

lak and lagan are very close in meaning and often interchangeable.
Both can mean easy (for tasks, exams) and light (for weight).

In standard usage, lak is very common and a bit shorter and more neutral; lagan can sometimes feel slightly more descriptive or stylistic, but in everyday speech you’ll hear both. In this sentence, either adjective works.

How is the whole sentence pronounced?

A simple pronunciation guide (stressed syllables in CAPS; č/ć like English “ch”):

TADA smo poMIS-li-li da ĆE IS-pit BI-ti LAK.

More precisely in IPA (approximate):

[ˈta.da smo pɔˈmis.li.li da t͡ʃe ˈis.pit ˈbi.ti lak]

Clitics like smo and će are unstressed and blend quickly with surrounding words.