Learn Hardcore Croatian: Kad je vrijeme lijepo, sjedimo u parku. - When the weather is nice, we sit in the park.

They mean the same thing: when. Kad is simply a shorter form of kada. Both are standard; kad is more common in everyday speech, kada can feel a bit more formal or emphatic. You can use either here with no change in meaning.

Why is there a comma after the first clause?

Because the subordinate clause (Kad je vrijeme lijepo) comes first. In Croatian, when a subordinate clause precedes the main clause, you put a comma before the main clause: Kad je vrijeme lijepo, sjedimo u parku.
If the main clause comes first, a comma is usually not used: Sjedimo u parku kad je vrijeme lijepo.

Why is je right after kad? Could I say Kad vrijeme je lijepo?

No. Je (the 3rd person singular of biti = to be) is a clitic and follows the “second position” rule: it must come in the second slot in its clause. So you get Kad je vrijeme lijepo, not Kad vrijeme je lijepo.

Why is it lijepo and not lijep?

Because vrijeme (weather/time) is a neuter noun. Adjectives agree in gender and number with the noun, so you use the neuter singular form lijepo.

Masculine: lijep dan
Feminine: lijepa noć
Neuter: lijepo vrijeme

Can I also say Kad je lijepo vrijeme instead of Kad je vrijeme lijepo?

Yes. Both are correct.

Kad je lijepo vrijeme sounds like the fixed phrase “when the weather is nice.”
Kad je vrijeme lijepo is a neutral word order stating “when the weather is nice.”
Meaning-wise, there’s no real difference here.

Can I drop vrijeme and just say Kad je lijepo, …?

Yes. Kad je lijepo, … is very natural and means “When it’s nice (out), …,” with “weather” understood from context.

Does vrijeme mean weather or time here?

It can mean both in general, but here it clearly means “weather.” Context and common collocations decide the meaning. With adjectives like lijepo, ružno, sunčano, it usually refers to weather.

What does sjedimo express—habit or what’s happening right now?

Croatian present covers both. In this sentence with kad/kada, it’s habitual/general: “When the weather is nice, we (tend to) sit in the park.”
For “right now,” you’d use context words: Sada sjedimo u parku.

What’s the difference between sjedimo, sjednemo, and sjedamo?

sjedimo (from sjediti) = “we sit/are sitting” (a state).
sjednemo (from perfective sjesti) = “we sit down” (a single completed action).
sjedamo (from imperfective sjedati) = “we (habitually) sit down” or “we are in the process of sitting down.”
Examples:
Kad je vrijeme lijepo, sjedimo u parku.
Dođemo, pa sjednemo na klupu.
Svako jutro sjedamo za stol.

Why is it u parku and not u park?

Because of case and meaning with u:

Static location (in/on a place) → u
- locative: u parku = “in the park.”
Motion into (to/into a place) → u
- accusative: u park = “(to) the park.”
  So: Sjedimo u parku, but Idemo u park.

Why use u and not na here?

With places like a park, you’re typically considered “inside” the area, so u parku (“in the park”) is standard. Croatian prepositions are partly idiomatic:

u: u parku, u šumi, u kafiću
na: na trgu, na ulici, na plaži, na stadionu

There’s no “a/the” in Croatian. How do I know if it means “in a park” or “in the park”?

Croatian has no articles. U parku can translate as either “in a park” or “in the park.” Context decides which is more natural in English.

Why is there no mi (“we”)?

Croatian usually omits subject pronouns because the verb ending tells you the person/number. Sjedimo ends in -mo, which already means “we.” You can add Mi for emphasis: Mi sjedimo u parku.

How do I pronounce the tricky parts?

kad je: “kahd yeh”
vrijeme: approx “vr-YEH-meh” (roll the r lightly; the ije is like “yeh”)
sjedimo: “SYEH-dee-mo” (the sj yields a “sy” sound)
u parku: “oo PAHR-koo”
Keep syllables clear; Croatian pronunciation is quite phonetic.

Can I use ako instead of kad?

Not here. Kad/kada = “when” (time reference), often “whenever” in habitual statements. Ako = “if” (a condition/uncertainty).

Correct: Kad je vrijeme lijepo, sjedimo u parku. (“whenever/when”)
Different meaning: Ako je vrijeme lijepo, sjedimo u parku. (“if it’s nice, then we sit…”)—this sounds like a plan/condition, not a general habit.

How would I say this about the future?

Use future forms or bude in the time clause:

Kad bude lijepo vrijeme, sjedit ćemo u parku.
Kad bude lijepo, sjedit ćemo u parku.
You can also keep the present in the time clause: Kad bude proljeće, sjedit ćemo u parku.