Learn Hardcore Croatian: Preko vikenda često idemo u park. - Over the weekend we often go to the park.

preko is a preposition meaning over, across, via, and in time expressions it often means during / over.
vikenda is the genitive singular of vikend (weekend). The preposition preko always takes the genitive case, which is why it is vikenda, not vikend.

So the structure is: preko + genitive → preko vikenda = over the weekend.

Could I just say vikendom instead of preko vikenda?

Yes, you can.

Vikendom means on weekends / at weekends, and it suggests a general, repeated action.
Preko vikenda also sounds like something habitual here, but it can more easily refer to a specific coming weekend as well, depending on context.

Both are natural. For a general habit, all of these work:

Preko vikenda često idemo u park.
Vikendom često idemo u park.
Za vikend često idemo u park. (very common in speech)

Why is it idemo, and what form of the verb is that?

Idemo is the 1st person plural present tense of the verb ići (to go).

ići – to go (imperfective)
mi idemo – we go / we are going

The sentence Preko vikenda često idemo u park. is in the present tense describing a habitual action:

we often go to the park over the weekend.

What is the function of često, and where can it go in the sentence?

Često means often and is an adverb of frequency.

In this sentence it appears as:

Preko vikenda često idemo u park.

You can move često around a bit without changing the meaning much:

Često preko vikenda idemo u park.
Preko vikenda idemo često u park. (possible, but the most neutral is with često before the verb: često idemo)

Positioning it directly before the verb (često idemo) is the most natural and common.

Why is it u park and not u parku?

Because the verb shows movement towards a place.

The preposition u can take:

Accusative for movement into / to something → u park (to the park)
Locative for being in a place → u parku (in the park)

So:

Idemo u park. – We are going to the park. (destination → accusative: park)
Mi smo u parku. – We are in the park. (location → locative: parku)

What case is park in, and why?

In u park, the noun park is in the accusative singular.

Reason:

u
- accusative = movement into / to a place.
park is a regular masculine noun; nominative park, accusative is also park (same form, different function).

So u park = into the park / to the park.

How would the sentence change if we wanted to say We often are in the park over the weekend rather than go to the park?

You would change the verb and the case after u:

Preko vikenda često smo u parku.
- smo = we are (1st person plural of biti – to be)
- u parku = in the park (u
  - locative: parku)

Compare:

često idemo u park → we often go to the park (movement)
često smo u parku → we are often in the park (location)

Is the word order Preko vikenda često idemo u park fixed, or can I move parts around?

Croatian word order is relatively flexible, and you can move elements for emphasis. Some natural variants:

Često preko vikenda idemo u park. (emphasis a bit more on često)
U park često idemo preko vikenda. (emphasis on u park)

However, the original:

Preko vikenda često idemo u park.

is the most neutral and typical. The key rules:

Keep the verb relatively early.
Keep često close to the verb.
Don’t split preko from vikenda.

Is there a difference between preko vikenda and tijekom vikenda?

Both can mean during the weekend / over the weekend, but there is a nuance:

Preko vikenda – very common in everyday speech; sounds neutral and conversational.
Tijekom vikenda – a bit more formal or bookish; more common in written language, announcements, etc.

In normal conversation, preko vikenda or za vikend are more typical than tijekom vikenda.

How do you pronounce idemo and često?

Approximate pronunciation (IPA):

idemo → /îdemo/
- i as in machine
- stress on i: Í-de-mo
često → /t͡ʃêsto/
- č as in ch in church
- e as in bed, stress on čé: ČÉ-sto

Is idemo used only for walking, or can it also mean going by car, bus, etc.?

Ići / idemo is neutral about the means of transport. It just means to go.

Idemo u park. – We’re going to the park. (could be on foot, by car, by bus…)

If you want to specify the means, you add another expression:

Idemo autom u park. – We’re going to the park by car.
Idemo autobusom u park. – We’re going to the park by bus.

How would I say I often go to the park over the weekend instead of we?

Change the verb and pronoun to 1st person singular:

Preko vikenda često idem u park.
- idem = I go / I am going (1st person singular present of ići)

So:

Preko vikenda često idemo u park. – We often go to the park over the weekend.
Preko vikenda često idem u park. – I often go to the park over the weekend.