Learn Hardcore Croatian: Kutija u sredini police je teška, jer je puna rajčica iz vrta. - The box in the middle of the shelf is heavy because it is full of tomatoes from the garden.

u – preposition meaning “in”, here it governs the locative case.
sredini – locative singular of sredina (middle) → u sredini = “in the middle.”
police – genitive singular of polica (shelf).

The pattern is:

u + locative to say “in (the) middle”
then genitive to say “of what” → sredina police = “the middle of the shelf”.

So u sredini police = “(located) in the middle of the shelf.”

Why does police look plural, but you say it is singular here?

The form police is ambiguous in Croatian; it can be:

nominative plural of polica (shelf) → police = shelves
genitive singular of polica (shelf) → police = of the shelf

In u sredini police, the context and grammar tell you it must be genitive singular:

u sredini already uses the locative on sredina.
The noun after sredina is expected in genitive: sredina police = “the middle of the shelf.”

So even though police looks like plural, here it is genitive singular: “of the shelf,” not “of the shelves.”

Can I say na sredini police instead of u sredini police? Is there a difference?

Both are possible and common:

na sredini police – literally “on the middle of the shelf”
u sredini police – literally “in the middle of the shelf”

In practice:

For a flat surface like a shelf, na sredini police is probably slightly more natural, because na is “on (a surface).”
u sredini police emphasizes more the area / region in the middle rather than the top surface, but in everyday language people often use it quite freely, and it doesn’t sound wrong.

So yes, you can safely say na sredini police here, and u sredini police is also acceptable. The meaning is essentially the same in this sentence.

Why is there a comma before jer? Do we always put a comma before jer?

In standard Croatian, you do put a comma before jer when it introduces a reason clause.

Kutija u sredini police je teška, jer je puna rajčica iz vrta.
→ main clause: Kutija … je teška
→ subordinate clause: jer je puna rajčica iz vrta

The comma separates the main clause from the subordinate clause introduced by jer (“because”).

In normal written Croatian:

You almost always write a comma before jer when it means “because.”
Only in very short, fixed expressions might it occasionally be omitted, but as a learner you should always use the comma in this kind of sentence.

Why is teška feminine, and how does it relate to kutija?

In Croatian, adjectives must agree with the noun they describe in:

gender
number
case

Here:

kutija is feminine, singular, nominative (subject).
The adjective težak must match that, so it becomes:
- masculine: težak
- feminine: teška
- neuter: teško

Since kutija is feminine singular, we say:

Kutija … je teška. – “The box is heavy.”

So teška is just the feminine, singular, nominative form agreeing with kutija.

Why is it težak in masculine but teška in feminine? Why does the spelling change?

The masculine base form is:

težak – “heavy” (masculine)

The feminine is:

teška – “heavy” (feminine)

So ž becomes š in the feminine form. This is due to a regular sound change when forming some adjective forms: the combination that would be written žk is pronounced like šk, and Croatian spelling reflects that pronunciation.

You don’t need to master the phonological rule right away; just memorize the pattern:

težak (m.) → teška (f.) → teško (n.)

Other adjectives show similar alternations (e.g. blizak → bliska). The important point is: teška is the correct feminine form of težak, not a spelling mistake.

Why is puna also feminine, and why is je repeated: je teška, jer je puna …?

puna agrees with kutija:

The adjective is pun (full).
Feminine singular nominative: puna.
It describes the same noun kutija, so it must match its gender and number.

So:

Kutija … je teška – “The box is heavy”
(Kutija) je puna rajčica – “(The box) is full of tomatoes”

Why is je repeated?

The sentence has two separate clauses:

Kutija u sredini police je teška
jer je puna rajčica iz vrta

Each clause needs its own verb je (“is”):

first je goes with teška
second je goes with puna

You cannot normally drop the second je here.
✗ Kutija … je teška, jer puna rajčica iz vrta. sounds incomplete or wrong.

Why is it puna rajčica (genitive plural) and not puna rajčice?

The noun rajčica (tomato) has forms:

nominative singular: rajčica
genitive singular: rajčice
nominative plural: rajčice
genitive plural: rajčica

The adjective pun (“full”) normally takes a genitive after it:

puna čega? – full of what? → genitive

Now you choose singular or plural based on meaning:

puna rajčice → genitive singular: “full of (one) tomato” (or of tomato as a single mass)
puna rajčica → genitive plural: “full of tomatoes” (many pieces)

In the sentence, the idea is “full of tomatoes (many),” so genitive plural is used:

puna rajčica = “full of tomatoes.”

Could I say puna rajčicama instead of puna rajčica?

No, not with the adjective pun.

puna rajčica – correct, uses genitive plural after pun.
puna rajčicama – incorrect here; rajčicama is instrumental plural.

Compare:

Kutija je puna rajčica. – “The box is full of tomatoes.” (adjective pun
- genitive)
Napunio je kutiju rajčicama. – “He filled the box with tomatoes.” (verb napuniti
- instrumental)

So:

With pun(a) → use genitive (puna rajčica).
With verbs like napuniti (“to fill”) → often use instrumental (napuniti kutiju rajčicama).

Why is it iz vrta and not od vrta or s vrta?

All three prepositions can mean “from” in English, but they’re used differently.

iz
- genitive
  – “from the inside of, out of”
  – iz vrta = “from (out of) the garden”
  Very normal if you think of the garden as a bounded area you are taking things from.
s / sa
- genitive
  – “from off (a surface), from (a place/area, often flat or elevated)”
  – s vrta is also heard in everyday speech and can mean “from the garden” too.
  Common phrase: povrće s vrta – vegetables from the garden.
od
- genitive
  – “from” in the sense of origin/source, possession, cause, distance
  – od vrta would more likely mean “from the garden (as a point of distance)” and sounds odd for produce: you wouldn’t say rajčice od vrta.

In this sentence, iz vrta is perfectly natural: rajčica iz vrta = “tomatoes from the garden.”
You will also frequently hear rajčice s vrta with almost the same meaning.

What case is vrta in iz vrta, and how does iz work?

vrta is genitive singular of vrt (garden).

The preposition iz always takes the genitive:

iz vrta – from the garden
iz kuće – from the house
iz škole – from school
iz kutije – from the box

So the pattern is:

iz + genitive → “out of / from (inside) something”

Here: iz vrta → “from the garden.”

Can the word order be changed in this sentence? For example, where can u sredini police and iz vrta go?

Croatian word order is fairly flexible, so you can move phrases for emphasis without changing the basic meaning.

All of these are grammatical:

Kutija u sredini police je teška, jer je puna rajčica iz vrta. (original)
U sredini police kutija je teška, jer je puna rajčica iz vrta.
Kutija je u sredini police i teška je, jer je puna rajčica iz vrta.
Kutija u sredini police je teška, jer je puna rajčica iz vrta. (you could also move iz vrta earlier)
… jer je puna rajčica iz vrta. → … jer je puna iz vrta rajčica. (this last one is possible but sounds marked/emphatic)

Natural, neutral versions usually keep:

subject near the beginning (Kutija …)
adverbial phrases like u sredini police after the subject or at the very start
iz vrta immediately after the noun it modifies: rajčica iz vrta

So the original order is a clear, neutral choice.

How do I pronounce rajčica, and what are the sounds č and c in this sentence?

Key sounds:

č – like “ch” in English “church” (always hard, never like “sh”)
c – like “ts” in English “cats”
j – like “y” in “yes”

Word by word:

Kutija – KOO-tee-ya
u – like English “oo” in “food”
sredini – roughly sre-DEE-nee (rolled r)
police – PO-li-tse (the c is ts)
je – like English “yeh”
teška – TESH-ka (š = English “sh”)
jer – “yer” (short, with rolled r)
puna – POO-na
rajčica – roughly RAI-chit-sa:
- raj – like English “rye” (but with j = “y”)
- či – chee
- ca – tsa
iz – iz (like “is” but with clear z)
vrta – VR-ta (rolled r)

Said smoothly:
Kutija u sredini police je teška, jer je puna rajčica iz vrta.