Learn Hardcore Croatian: Novi autobus je najbrži u gradu. - The new bus is the fastest in the city.

Croatian usually prefers Subject – Verb – Predicate, but there is an extra rule: short forms of “to be” (sam, si, je, smo, ste, su) behave as clitics and like to stand in the second position of the clause.

In Novi autobus je najbrži u gradu.

Novi autobus is the first “chunk” (the subject),
so je comes right after it.

You generally cannot start a normal statement with je in Croatian (Je novi autobus… is wrong in standard language).

Can I also say Novi je autobus najbrži u gradu?

Yes, Novi je autobus najbrži u gradu is also grammatically correct.

Here je is still in second position, but now after the first word (Novi) instead of after the whole subject phrase Novi autobus.
Both versions are understood the same; Novi je autobus… can slightly highlight novi (“the new bus is the fastest”), but the difference is subtle in everyday speech.

What exactly does je mean here, and can it ever be left out?

Je is the 3rd person singular present form of biti (to be), so it corresponds to English “is”.

In standard Croatian you must keep “je” in sentences like this:

✔ Novi autobus je najbrži u gradu.
✘ Novi autobus najbrži u gradu. (incorrect in normal prose/speech)

Unlike some Slavic languages, Croatian does not normally drop the present tense of biti in such sentences.

What form is najbrži, and how is it formed from brz?

Najbrži is the superlative of the adjective brz (fast).

The pattern is:

positive: brz (fast)
comparative: brži (faster)
superlative: najbrži (fastest) → naj-
- comparative

So in Novi autobus je najbrži u gradu, najbrži means “the fastest”.

Why is it najbrži and not najbrže or najbrža?

Again, this is adjective agreement. Najbrži is:

masculine,
singular,
nominative,

because it describes the subject autobus, which is masculine singular nominative.

If the subject were:

feminine: Nova linija je najbrža u gradu.
neuter: Novo vozilo je najbrže u gradu.

Why is it u gradu and not u grad?

The preposition u can take two different cases depending on meaning:

Accusative for motion towards something: Idem u grad. (I’m going to the city.)
Locative for location / being in something: Živim u gradu. (I live in the city.)

In Novi autobus je najbrži u gradu, we are talking about where it is the fastest (in the city), not movement, so u + locative is used → u gradu.

What case is gradu, and what is the base form of this noun?

The base (dictionary) form is grad – nominative singular.

Gradu is the locative singular of grad.
A simplified part of the paradigm looks like:

Nominative: grad (city)
Genitive: grada
Dative: gradu
Accusative: grad
Locative: gradu → used after u when it means “in”
Instrumental: gradom

So u gradu literally means “in (the) city”.

There is no word for “the” in this sentence. How do we know it means “the new bus” and “the fastest”?

Croatian has no articles (no direct equivalents of “a/an/the”). Definite vs. indefinite meaning is usually understood from:

context,
word order,
use of superlatives, possessives, etc.

With superlatives like najbrži, the meaning is usually definite: najbrži is naturally understood as “the fastest (one)”.
So Novi autobus je najbrži u gradu is understood as “The new bus is the fastest in the city.”

Can I say Novi autobus je najbrži autobus u gradu, or is that wrong?

You can say Novi autobus je najbrži autobus u gradu; it is grammatically correct.

However, it is a bit repetitive, because najbrži already implies “the fastest bus” in this context.
The shorter version Novi autobus je najbrži u gradu is more natural and typical unless you want extra emphasis or clarity.

Could Novi autobus mean “the new bus line” rather than a single physical bus?

Literally, autobus is a bus (vehicle).

In everyday speech, people might sometimes use autobus loosely for “that bus service/line,” but if you clearly mean a bus line, you would usually say something like:

nova autobusna linija (new bus line)

So Novi autobus je najbrži u gradu is normally understood as a particular new bus (vehicle) being the fastest in the city.

How would the sentence change if the subject were feminine, like “tram line”?

Take tramvajska linija (tram line), which is feminine singular:

Nova tramvajska linija je najbrža u gradu.
- nova – feminine singular nominative of nov
- tramvajska linija – feminine noun phrase
- je – 3rd person singular of biti
- najbrža – feminine singular nominative of najbrz(a)
- u gradu – “in the city” (locative)

This shows how both adjectives (nova, najbrža) change form to agree with a feminine noun instead of autobus.