Learn Hardcore Croatian: Kad je vani kiša, radije idem u teretanu nego trčati u parku. - When it is raining outside, I prefer to go to the gym rather than run in the park.

In Croatian, saying je kiša (literally “is rain”) is a normal way to say “it is raining / it’s rainy.”
vani is an adverb meaning “outside, outdoors.” Adverbs like this usually come after the verb je.
Croatian doesn’t need a dummy subject like English “it”; you just say je kiša, not “it is rain.”

So the structure is perfectly normal Croatian, even though a literal English translation sounds strange.

What’s the difference between kad and kada? Could we say Kada je vani kiša?

Yes, you can absolutely say Kada je vani kiša; it means the same thing.

kad – shorter, more colloquial, very common in speech and informal writing.
kada – slightly more formal or emphatic, more common in writing, but also used in speech.

In this sentence, both are correct:

Kad je vani kiša, radije idem u teretanu…
Kada je vani kiša, radije idem u teretanu…

The choice is mostly about style and rhythm, not grammar or meaning.

Why is there a comma after kiša?

The comma separates a subordinate clause from the main clause.

Subordinate temporal clause: Kad je vani kiša – When it’s raining outside
Main clause: radije idem u teretanu nego trčati u parku – I’d rather go to the gym than run in the park

In Croatian, when a subordinate clause comes before the main clause, you must put a comma between them:

Kad je vani kiša, radije idem u teretanu…
If you reverse the order, the comma is often optional:
Radije idem u teretanu nego trčati u parku kad je vani kiša.

So the comma is there for the standard reason: clause boundary.

Why do we say idem u teretanu and not idem na teretanu?

Because of how Croatian uses the prepositions u and na:

u is usually used for enclosed spaces, rooms, buildings, and “inside” locations:
- u teretanu – to the gym
- u školu – to (the) school
- u kuću – into the house
na is often used for surfaces, open areas, and many institutions/events:
- na stol – onto the table
- na posao – to work
- na fakultet – to the university (institution)
- na koncert – to the concert

A teretana (gym) is understood as an indoor space you go into, so native speakers say:

Idem u teretanu. – I’m going to the gym.

Na teretanu sounds wrong in standard Croatian in this meaning.

Why is it u teretanu but u parku? Why different endings?

This shows the typical pattern with u:

u + accusative = movement into / to a place
u + locative = location in / at a place

In the sentence:

idem u teretanu
- idem = I go (movement)
- u + teretanu (accusative) = to the gym (destination)
trčati u parku
- trčati = to run (activity happening somewhere)
- u + parku (locative) = in the park (location)

Forms:

Nominative: teretana, park
Accusative: teretanu, park
Locative: teretani, parku

So:

u teretanu = into / to the gym (direction)
u parku = in the park (where the running happens)

If you wanted direction with park, you’d also use accusative: u park = to the park.

Could we say više volim ići u teretanu nego trčati u parku instead of radije idem u teretanu? Is there a difference?

Yes, you can say that, and the meaning is almost the same:

Radije idem u teretanu nego trčati u parku.
Više volim ići u teretanu nego trčati u parku.

Differences in nuance:

radije is the comparative of the adverb rado (gladly, willingly).
- It sounds like “I rather / would rather”, focusing on your choice in that situation.
više volim literally means “I love/like more”.
- It points more directly to preference as a general fact.

In this particular sentence, both work very naturally and both can describe a general preference. Very often they’re interchangeable in practice.

One warning: don’t say više radije – that’s like saying “more rather” and is usually incorrect or at least very odd.

Why is radije placed before idem? Could it go in a different position?

Default word order places radije before the verb:

Radije idem u teretanu… – I’d rather go to the gym…

But you can move it, with some changes in emphasis:

Radije idem u teretanu nego trčati u parku.
– neutral, most natural.
Idem radije u teretanu nego trčati u parku.
– also correct; slightly more focus on idem (“It’s going that I rather do…”).
Idem u teretanu radije nego trčati u parku.
– still possible, putting radije near the comparison nego; sounds a bit more marked.

All three are understandable, but version 1 is the most typical and feels the smoothest. Croatian allows quite flexible word order, but moving radije changes rhythm and subtle focus, not the basic meaning.

Why is it nego trčati u parku and not nego trčim u parku? Can we use da there, like nego da trčim u parku?

What’s happening here is ellipsis (omitting repeated words):

Full version could be:
Radije idem u teretanu nego [da idem] trčati u parku.

Since the subject (I) and tense are already clear, Croatian often drops the repeated verb and uses an infinitive:

radije idem u teretanu nego trčati u parku
– literally “rather I go to the gym than run in the park.”

Alternatives:

Radije idem u teretanu nego da trčim u parku.
- Completely correct and natural.
- Uses nego da + present instead of infinitive.
Radije idem u teretanu nego trčim u parku.
- This is usually felt as incorrect or at least very unnatural in standard language.
- You normally don’t have finite verb forms (like trčim) directly after nego in this type of comparison unless there’s a full second clause clearly structured.

So the good options are:

…nego trčati u parku.
…nego da trčim u parku.

The version in your sentence (with trčati) is very common and perfectly idiomatic.

Do we really need vani? Could we just say Kad je kiša?

You don’t strictly need vani. These are all possible:

Kad je kiša, radije idem u teretanu…
Kad je vani kiša, radije idem u teretanu…
Kad pada kiša, radije idem u teretanu…

Differences:

Kad je kiša – very common, means roughly “when it’s rainy / when it’s raining”.
Kad je vani kiša – adds the explicit idea “outside”, but of course rain is normally outside anyway; it just sounds a bit more descriptive.
Kad pada kiša – literally “when rain is falling”, i.e. “when it’s raining.”

All are natural. Vani here is extra information, not grammatically required.

What’s the difference between trčati u parku and trčati po parku?

Both are correct but have slightly different nuances:

trčati u parku – to run in the park
- Neutral statement of location: where the action happens.
- Focus is simply: the place of running is the park.
trčati po parku – literally to run across/around the park
- Emphasizes movement over the area, around various parts of the park.
- Often feels a bit more dynamic: running around inside that space.

In your sentence, trčati u parku is perfectly natural and probably the most straightforward version.

Why are present tense forms (je, idem) used to talk about a general habit, instead of future tense like ću ići?

Croatian uses the present tense very often for:

general truths
habits
repeated situations

Here we have a typical habitual pattern:

Kad je vani kiša, radije idem u teretanu…
– Whenever it’s raining outside, I (usually) prefer going to the gym…

This matches English present simple “When it’s raining… I go…”.

If you said:

Kad bude vani kiša, ići ću u teretanu…

you’d be talking about a specific future situation (something like: “When it is (at some point) raining outside, I will go to the gym.”). That’s not a general habit anymore, but a particular plan or prediction.

So the simple present je / idem is exactly the right tense for a general preference or habit.

Could we move the “when” part to the end: Radije idem u teretanu nego trčati u parku kad je vani kiša? Does that change anything?

Yes, we can, and it’s still correct:

Kad je vani kiša, radije idem u teretanu nego trčati u parku.
Radije idem u teretanu nego trčati u parku kad je vani kiša.

Both mean the same thing.

Subtle differences:

With Kad je vani kiša at the beginning, you first set up the condition, then state your reaction/preference.
With kad je vani kiša at the end, the sentence starts with your general preference, and then you add under what condition it applies.

Grammatically, both are fine. In speech, people use both orders; the initial Kad je vani kiša, … might sound slightly more structured or “neat,” especially in written style.