Learn Hardcore Croatian: On pokazuje svoje fotografije s mosta. - He is showing his photographs from the bridge.

On pokazuje svoje fotografije s mosta. – He is showing his photos from the bridge.
Pokazuje svoje fotografije s mosta. – Same meaning; on is just omitted.

We usually keep On:

when we want to emphasize he (and not someone else), or
in the first example in a text, before it is clear who we are talking about.

Otherwise, it’s very natural simply to say: Pokazuje svoje fotografije s mosta.

What is the difference between pokazuje and pokazati / pokazivao je?

The verb pokazivati (imperfective) and pokazati (perfective) form an aspect pair.

pokazivati – to be showing, to show repeatedly, to show over some time
- On pokazuje svoje fotografije. – He is showing his photos / He shows his photos (habitually).
pokazati – to show (once, as a completed act)
- On će pokazati svoje fotografije. – He will show his photos (one completed act).
- On je pokazao svoje fotografije. – He showed his photos.

Pokazuje is:

present tense
3rd person singular
of pokazivati (imperfective).

So On pokazuje… corresponds to He is showing… / He shows… in English.

Why is it svoje fotografije and not njegove fotografije?

Croatian has a special reflexive possessive adjective svoj (my own / your own / his own / her own / their own etc.) that you must use when the possessor is the same as the subject.

Here the subject is On (he), and the photos belong to that same he.

So we use svoje:

On pokazuje svoje fotografije.
= He is showing his own photos.

If you say:

On pokazuje njegove fotografije.

this usually means:

He is showing his photos where his = some other man’s photos, not the subject’s.

So:

svoje fotografije – his own photos (subject = owner)
njegove fotografije – some other guy’s photos (owner ≠ subject)

Why exactly svoje (this form) and not svoj or svoga?

Svoj is an adjective and must agree with the noun it describes in:

gender
number
case

The noun is fotografije:

fotografija – feminine, singular
fotografije – feminine, plural (here: accusative plural as the direct object)

For feminine accusative plural, the form of svoj is svoje.

So:

svoj – basic dictionary form (masculine singular nominative)
svoje fotografije – correct form for feminine plural accusative.

Compare:

Vidim svoju fotografiju. – I see my (own) photo. (fem. sing. acc.)
Vidim svoje fotografije. – I see my (own) photos. (fem. pl. acc.)

What case is fotografije in, and why?

In On pokazuje svoje fotografije s mosta, fotografije is:

feminine
plural
accusative

Reason: fotografije is the direct object of the verb pokazuje (What is he showing? – photos).

In Croatian, direct objects of transitive verbs are normally in the accusative case.

Singular vs. plural:

(On) pokazuje svoju fotografiju. – one photo (accusative singular: fotografiju)
(On) pokazuje svoje fotografije. – several photos (accusative plural: fotografije)

Does s mosta mean “from the bridge” or “on the bridge”?

s mosta means from the bridge (off / from that location).

s(a) + genitive often expresses movement from a surface or elevated place:
- s mosta – from the bridge
- sa stola – from the table
- s krova – from the roof

To say on the bridge (location), you would normally use na + locative:

na mostu – on the bridge

So:

On pokazuje svoje fotografije s mosta.
→ He is showing his photos from the bridge (i.e., the photos were taken from the bridge, or they show views from the bridge).
On pokazuje svoje fotografije na mostu.
→ He is on the bridge and is showing his photos there (location).

Why is it s mosta and not sa mosta? Are both correct?

Both s mosta and sa mosta are grammatically correct.

The preposition is s (short) or sa (longer variant). Sa is often used:

before words starting with s, z, š, ž to avoid tongue-twisters
before some consonant clusters for easier pronunciation.

For mosta, both are easy to pronounce, so you will hear:

s mosta – quite common and perfectly normal
sa mosta – also correct, sometimes sounds a bit more “careful” or dialect-influenced.

In standard language, s mosta is very natural.

Why is it mosta and not just most?

The noun most (bridge) is in the genitive singular here, because the preposition s(a) in the meaning from (a surface / elevated place) governs the genitive case.

Declension (singular) of most:

nominative: most – the bridge
genitive: mosta – of the bridge / from the bridge

So:

Most je dugačak. – The bridge is long. (nominative)
S mosta se vidi rijeka. – From the bridge, you can see the river. (genitive after s)

In our sentence:

s (preposition) + mosta (genitive) → s mosta

Is the s in s mosta the same s as in s tobom (“with you”)?

Formally it’s the same preposition s, but it has different meanings and different cases:

s(a) + genitive – from (movement down/from a surface or place)
- s mosta – from the bridge
- sa stola – from the table
- s krova – from the roof
s(a) + instrumental – with (together with someone/something)
- s tobom – with you
- s prijateljima – with (my) friends
- s djecom – with the children

So:

In s mosta, mosta is genitive → meaning from the bridge.
In s tobom, tobom is instrumental → meaning with you.

Can the word order change? For example, can I say On s mosta pokazuje svoje fotografije?

Yes, Croatian word order is relatively flexible, and On s mosta pokazuje svoje fotografije is grammatically correct.

Different orders can slightly change focus or style:

On pokazuje svoje fotografije s mosta.
– neutral; we just state what he is doing and add that the photos are from the bridge.
On s mosta pokazuje svoje fotografije.
– now s mosta is closer to the verb; it can sound more like:
From the bridge, he is showing his photos (small emphasis on “from the bridge”).

Other possible orders:

S mosta on pokazuje svoje fotografije. – Strong focus on from the bridge.
Svoje fotografije s mosta on pokazuje. – Emphasis that it is his (own) photos from the bridge that he is showing.

All are possible, but the original sentence is the most neutral and typical.