Learn Hardcore Croatian: Vodič mirno objašnjava smjer svim putnicima u autobusu. - The guide calmly explains the direction to all the passengers on the bus.

Vodič – subject (the guide)
mirno – adverb (calmly) modifying the verb
objašnjava – main verb in the present tense (explains / is explaining)
smjer – direct object in the accusative case (the direction / route)
svim putnicima – indirect object in the dative plural (to all (the) passengers)
u autobusu – prepositional phrase in the locative (in/on the bus)

So the structure is: [subject] [adverb] [verb] [direct object] [indirect object] [location].

Why is smjer in that form? Is it a special case?

Smjer is the direct object of the verb objašnjava, so it is in the accusative singular.

Nominative (dictionary form): smjer – direction, route
Accusative singular (for most masculine inanimate nouns): smjer – same form as nominative

So even though it looks the same as the nominative, its function here is accusative because it’s what is being explained.

Why is it svim putnicima, not svi putnici?

Svi putnici = all (the) passengers as a subject (nominative plural).
Svim putnicima = to all (the) passengers as an indirect object (dative plural).

In this sentence, the passengers are not doing the action; they are receiving the explanation:

Vodič objašnjava smjer (kome?) svim putnicima.
The guide explains the direction (to whom?) to all the passengers.

So we need the dative plural:

svi putnici → svim putnicima (dative plural of putnik).

What case is svim putnicima, and what does it usually express?

Svim putnicima is in the dative plural.

The dative in Croatian often expresses:

to/for someone as an indirect object
- Objašnjava smjer svim putnicima. – He explains the direction to all the passengers.
beneficiary or recipient
- Daje kartu putniku. – He gives the ticket to the passenger.

The ending -ima / -ima or -ima / -ama is typical for dative plural:

putnik → putnicima
student → studentima

What case is u autobusu and why do we use that form instead of u autobus?

U autobusu uses the locative case (autobusu) with the preposition u, meaning in/on the bus (location).

Croatian u can take two cases:

Accusative – movement into something:
- ulazim u autobus – I’m getting on(to) the bus (into it)
Locative – location inside something:
- u autobusu – in/on the bus (already there)

Here the guide is already on the bus, so we use locative: u autobusu.

How is mirno formed, and why is it used here?

Mirno is an adverb meaning calmly.

It is formed from the adjective miran (calm) in a very common way:

adjective: miran – calm (a calm guide)
adverb: mirno – calmly (explains calmly)

Pattern (very simplified):

-an / -en / -an → -no
- miran → mirno
- tih → tiho (quiet → quietly)

We use mirno here to describe how the guide is explaining:

objašnjava mirno – explains calmly.

Does the adverb mirno have to come before the verb? Can I move it?

It doesn’t have to come before the verb. Croatian word order is quite flexible. These are all possible:

Vodič mirno objašnjava smjer svim putnicima u autobusu.
Vodič objašnjava smjer svim putnicima u autobusu mirno.
Vodič objašnjava mirno smjer svim putnicima u autobusu.

The default / neutral position is often before the verb or right after it, so the original is very natural.

Changing the position can slightly change the emphasis, but not the core meaning.

What exactly is the tense/aspect of objašnjava, and how does it compare to English?

Objašnjava is:

present tense,
of the imperfective verb objašnjavati (to be explaining, to explain repeatedly).

It can correspond to both:

He explains (habitual, general)
He is explaining (right now, ongoing)

English splits this into simple vs progressive; Croatian uses aspect plus context. Here, because the sentence feels like a current situation, you would usually translate it as:

The guide is calmly explaining the direction to all the passengers on the bus.

If you wanted a one-time, completed action, you’d use the perfective partner objasniti:

Vodič je mirno objasnio smjer svim putnicima.
– The guide calmly explained the direction to all the passengers. (finished action)

How do you conjugate objašnjavati in the present tense?

Infinitive: objašnjavati – to explain (imperfective)

Present tense (singular and plural):

ja objašnjavam – I explain / am explaining
ti objašnjavaš – you explain / are explaining (sg, informal)
on/ona/ono objašnjava – he/she/it explains / is explaining
mi objašnjavamo – we explain / are explaining
vi objašnjavate – you explain / are explaining (pl or formal)
oni/one/ona objašnjavaju – they explain / are explaining

In the sentence:

vodič objašnjava → he/she (the guide) explains / is explaining.

Is vodič masculine or feminine? How do you say “female guide”?

Vodič is grammatically masculine.

In practice:

vodič can refer to a male guide, or generically to a person who is a guide, if you don’t specify gender.
A specifically female guide is often vodičica (feminine form).

Examples:

Turistički vodič nam objašnjava grad.
– Our tour guide (male or unspecified) is explaining the city to us.
Turistička vodičica nam objašnjava grad.
– Our (female) tour guide is explaining the city to us.

In your sentence, vodič could be male or just unspecified; context would decide.

There are no words for “a” or “the”. How do you know if it’s “a guide” or “the guide”?

Croatian has no articles like English a/an or the.

Definiteness (a vs the) is understood from:

context – what has already been mentioned or is known
word order, pronouns, possessives, etc.

Your sentence could be translated as:

A guide is calmly explaining the direction…
The guide is calmly explaining the direction…

In most realistic contexts (like describing a tour), English would use the guide, but Croatian doesn’t mark this difference in the noun form.

Could I say svim putnicima autobusa instead of svim putnicima u autobusu?

Svim putnicima u autobusu is the natural, standard way to say to all the passengers on the bus.

Svim putnicima autobusa is grammatically possible, but sounds unnatural or at least unusual in everyday speech; it would literally be to all the passengers of the bus, and even that is normally expressed with u autobusu.

For location-based groups like passengers on a bus, in a train, in a plane, Croatian normally uses u + locative:

putnici u autobusu – passengers on the bus
putnici u vlaku – passengers on the train

So you should stick with svim putnicima u autobusu.

Can the word order change a lot, and will the meaning still be clear?

Yes, Croatian allows quite flexible word order because cases show the roles of words. For example, all of these are understandable:

Vodič mirno objašnjava smjer svim putnicima u autobusu.
Vodič objašnjava svim putnicima u autobusu smjer mirno.
Smjer vodič mirno objašnjava svim putnicima u autobusu.

They all mean essentially the same thing; you mostly change emphasis (what you highlight). The original word order is the most neutral and natural for standard speech.