Learn Hardcore Croatian: Moj otac radi u gradu.

Moj: possessive adjective meaning “my,” masculine nominative singular, agrees with otac.
otac: “father,” masculine noun, nominative singular (the subject).
radi: “works,” 3rd person singular present of the verb raditi (to work).
u: preposition “in,” which requires the locative case for location.
gradu: locative singular of grad (“city/town”), governed by u for a static location.

Why is it gradu and not grad?

Because u (“in”) expresses location here and takes the locative case. The noun grad in the locative singular becomes gradu. More examples:

u parku (in the park)
u kafiću (in the café)
u selu (in the village)
u kući (in the house)

When do I use u and when na?

u = “in/inside” (enclosed places, many buildings, cities): u gradu, u školi, u banci, u kazalištu.
na = “on/at” (open surfaces, events, institutions by convention): na selu (in the countryside), na poslu (at work), na fakultetu (at the university), na trgu (at the square), na plaži (at the beach). Some choices are idiomatic, so collocations must be learned.

How is radi formed, and how do I conjugate raditi?

Present tense of raditi (to work):

ja radim
ti radiš
on/ona/ono radi
mi radimo
vi radite
oni/one/ona rade

Negation: insert ne before the verb: ne radi (he doesn’t work). Past participles: radio (m), radila (f), radilo (n); used with je to make the past: On je radio (He worked/has worked). Aspect: raditi is imperfective; it covers both simple present and English present continuous depending on context.

Why isn’t there a word for “the” or “a”?

Croatian has no articles. Definiteness/indefiniteness is understood from context. Moj supplies possession; otherwise otac alone could mean “(a/the) father” depending on context.

Do I have to say moj? Could I just say Otac radi u gradu?

Moj otac radi u gradu is the clearest way to say “My father works in the city.”
Otac radi u gradu is possible, but without context it sounds generic (“Father works in the city”) rather than clearly “my father.”
Very natural alternative using dative-of-possession: Otac mi radi u gradu (“My father works in the city,” literally “Father to-me works…”). The clitic mi sits early in the sentence (second position).

What’s the difference between otac and tata?

otac = father (more formal/neutral)
tata = dad (informal, everyday) Both fit: Moj tata radi u gradu is common in casual speech.

How flexible is the word order?

Croatian allows movement for emphasis:

Neutral: Moj otac radi u gradu.
Emphasizing location: U gradu radi moj otac (implies: it’s in the city that my father works, not elsewhere).
Moj otac u gradu radi can work if you’re contrasting where he works with something else.
Meaning stays, but focus shifts. The fully neutral S–V–(place) order is most common for beginners.

How do I pronounce it?

Moj ≈ “moy” (j = English y).
otac ≈ “OH-tats” (c = ts; r is tapped/trilled in other words, but here there’s no r).
radi ≈ “RAH-dee.”
u ≈ “oo.”
gradu ≈ “GRAH-doo.”
Put a clear short vowel in each syllable; Croatian vowels are pure and consistent.

What case is otac, and how does it change in other cases?

Here otac is nominative singular (subject). Its key singular forms:

Nominative: otac (who? what?)
Genitive: oca (of father)
Dative: ocu (to/for father)
Accusative: oca (direct object)
Vocative: oče (addressing: “Father!”)
Locative: ocu (about/at father, with prepositions)
Instrumental: ocem (with/by father)

How would I say “My mother works in the city”?

Moja majka radi u gradu.
Note the agreement: moja (feminine), majka (feminine noun).

What changes if I talk about going to the city (motion), not being in it (location)?

Use u + accusative for motion:

Location: On radi u gradu. (He works in the city.)
Motion: On ide u grad. (He is going to the city.)

How do I say “My father works in Zagreb”?

Moj otac radi u Zagrebu.
City names also take the locative for location:

u Splitu
u Rijeci
u Osijeku

How do I say “My parents work in the city”?

Moji roditelji rade u gradu.
Note plural agreement: Moji (masculine plural), rade (3rd person plural of raditi).

Can radi mean something other than “works”?

Yes. Besides the verb raditi (“to work”), radi can also be a preposition meaning “because of/for the sake of” with the genitive:

Radi posla = because of work/for work’s sake.
In your sentence, radi is the verb form (not the preposition).

How would I ask “Where does your father work?”

Neutral: Gdje tvoj otac radi?
Very natural with clitic: Gdje ti otac radi?
Informal with “dad”: Gdje ti tata radi?
Polite/formal: Gdje vam otac radi?

Does grad mean city or town? How do I show “a” vs “the”?

Grad covers both “city” and “town.” Croatian lacks articles, so u gradu can mean “in the city” or “in a city.” Context disambiguates. If you want to say “in some city,” you can add nekom: u nekom gradu (“in some city”).

What’s the difference between u gradu and po gradu?

u gradu = in the city (location).
po gradu = around/throughout the city (movement or distribution): Šetamo po gradu (“We’re walking around the city”).