Learn Hardcore Croatian: Ona trči svaki dan ujutro u parku.

You can drop it. Croatian is a pro‑drop language, so the verb ending already shows person/number. Use Ona when you need clarity or emphasis/contrast.

Neutral: Trči svaki dan ujutro u parku.
Emphasis/contrast: Ona trči, a on hoda.

Why is it trči and not something else? How does trčati conjugate?

Trči is 3rd person singular present of trčati (to run). Present tense:

ja trčim
ti trčiš
on/ona/ono trči
mi trčimo
vi trčite
oni/one/ona trče

Does Croatian distinguish between “runs” and “is running”?

No. The simple present covers both ongoing and habitual actions. Context words do the work:

Habitual: (Ona) trči svaki dan ujutro…
Ongoing: (Ona) sada trči u parku.

For a one‑off completed act you’d use a perfective verb (e.g., potrčala je = she started to run).

Is svaki dan ujutro redundant? Can I just say svako jutro?

Both are correct:

svaki dan ujutro = every day, in the morning (explicitly daily + time of day)
svako jutro / svakog jutra = every morning (already implies daily) Stylistically, svako jutro is shorter and very common.

What’s the difference between svaki dan and svakog dana?

They mean the same (every day). Grammar/feel:

svaki dan: Accusative-of-time; very common, neutral.
svakog dana: Genitive; slightly more formal/literary or emphatic. Both are fine here.

Why is ujutro one word? Are ujutru/ujutra/jutrom also correct?

In standard Croatian, the adverb is written as one word: ujutro (in the morning).

ujutru is Serbian.
ujutra can mean “in the mornings” (habitually), but is less common in Croatian.
jutrom (instrumental) also means “in the mornings” and is idiomatic: Jutrom trči u parku.

Why is it u parku and not u park?

Because of motion vs. location:

u
- Locative = location (in/at): u parku = in the park.
u
- Accusative = direction (into/into): u park = into the park. Your sentence describes where the running happens (location), so Locative is required.

What case/ending is parku, and why that ending?

Parku is Locative singular of park (masculine). Many masculine nouns take -u in the Locative singular after u/na when indicating location:

u gradu (in the city), u selu (in the village), u kinu (at the cinema), u parku (in the park).

Can I say po parku instead of u parku?

You can, but the nuance changes:

u parku = in the park (neutral location).
po parku = around/all over the park (movement within the area, dispersed path). For a general jogging location, u parku is the neutral choice.

Should it be u parku or na parku? When do I use u vs. na?

With parks, use u parku. Rough guide:

u (in): enclosed or defined spaces/volumes (u parku, u školi, u kući).
na (on/at): surfaces, open venues, events (na plaži, na trgu, na stadionu, na koncertu). There are idiomatic exceptions, but this works here.

Can I change the word order? What are natural alternatives?

Croatian word order is flexible; information structure dictates placement. All of these are natural, with slightly different focus:

Ona trči svaki dan ujutro u parku. (neutral)
Svako jutro trči u parku. (time is fronted)
U parku trči svaki dan ujutro. (location is emphasized)
Ona svaki dan ujutro trči u parku. (time slot grouped before the verb)

Are there articles in Croatian? How do I say “in the park” vs. “in a park”?

Croatian has no articles; u parku can mean either “in the park” or “in a park.” Add a determiner if needed:

u tom parku (in that park)
u našem parku (in our park)

Does the verb show gender? Should I mark that she is female?

In the present tense, no gender marking appears. Gender shows in past/participle forms:

Jučer je trčala u parku. (she ran; feminine)
Jučer je trčao u parku. (he ran; masculine)

Any simpler way to say this?

Yes, two concise, very natural options:

Svako jutro trči u parku.
Trči u parku svako jutro. Both mean “She runs in the park every morning.”